Disorders of the inert structures: Capsular and non-capsular patterns

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Disorders of the inert structures

Capsular and non-capsular patterns

Chapter contents

Capsular pattern

The normal capsular pattern at the knee joint is gross limitation of flexion and slight limitation of extension; the ratio of flexion : extension is roughly 1 : 10 (Fig. 52.1). Thus 5° of limited extension corresponds to 45–60° limitation of flexion and 10° to 90–100°. The range of rotation becomes restricted only in advanced arthritis. Recently, the concept of a capsular pattern of motion restriction at the knee was supported by a study of patients with inflamed knees.¹

Fig 52.1 Capsular pattern at the knee joint.

A number of conditions of the knee show a limited range in a capsular way but all can be differentiated by findings from the history and clinical examination. Therefore, the important features of capsular disorders are a traumatic or non-traumatic, slow or sudden onset, synovial thickening, redness, nocturnal pain and so on.

Traumatic arthritis

Trauma to the capsule invariably leads to traumatic arthritis. Depending on the site and stage of the lesion, the capsular pattern may be gross (acute sprain of the medial collateral ligament) or more subtle (coronary sprain).

The diagnosis is relatively simple: after an injury, a capsular pattern appears, with effusion but no capsular thickening. Care must be taken not to overlook a traumatic haemarthrosis; when the question of blood in the knee joint does arise, diagnostic aspiration must be carried out at once. If blood is present in the aspirate, not only does it indicate a serious lesion but also the joint must be fully aspirated. On the other hand, if the aspirated fluid is clear, there is no point in emptying the joint because it is not the fluid that matters but the primary lesion. Hence treatment of traumatic arthritis showing a clear effusion only during aspiration involves dealing with the underlying primary disorder.

Rheumatoid and reactive arthritis

Rheumatoid arthritis is a common cause of knee inflammation. The symmetrical distribution of the affected joints is typical of this disease (Fig. 52.2).

Fig 52.2 The reactive (a) and rheumatoid (b) patterns of joint involvement.

Reactive arthritis is an inflammation of the joint secondary to a generalized infection but in which the articular fluid remains aseptic (Crohn’s disease, Reiter’s syndrome, aseptic gonococcal arthritis).2,3 The arthritis can remain monoarticular but may involve other joints in an asymmetrical manner.

In rheumatoid and reactive arthritis, intra-articular injections with triamcinolone give excellent but often only temporary results. Steroids injected into weight-bearing joints can cause arthropathy if injected too often.4,5 Therefore, injections must be restricted to two or three a year, which is enough to keep the patient comfortable. Nevertheless, considerable doubts about the dangers of repeated intra-articular steroid injections have arisen since a study report by Balch et al.⁶ They studied 65 patients with rheumatoid arthritis, who each received a minimum of 15 and a maximum of 167 injections at monthly intervals. Only two showed gross osteoarthrosis. These findings were confirmed later.⁷

Osteoarthrosis

The prime cause of gross degeneration in the knee joint is a disturbed distribution of load, which happens, for instance, when the patient suffers repeatedly from attacks of internal derangement because of a torn meniscus.8,9 Early osteoarthrosis will also occur if a valgus deformity is present from youth or there is an old malunited fracture that produces uneven load and repeated shearing strains. This also occurs if the meniscus is completely removed and its load-bearing function is therefore lost; the femoral condyles then exert pressure on the tibial platform over a much smaller area and the joint is apt to wear out rapidly.^10,11 The knee is often affected in osteitis deformans and marked osteoarthrosis can then supervene. Aseptic necrosis of the medial condyle has been blamed as the cause of rapidly progressive, symptomatic osteoarthrosis in the elderly.^12–14

The loss of articular cartilage, the structural changes of subchondral bone and the reactive osteophyte formation are the typical and well-known radiological appearances of progressive degenerative arthritis at the knee.¹⁵ It may be localized at the lateral, medial or patellofemoral compartment or may be generalized throughout the joint (Fig. 52.3).

Fig 52.3 Localized arthrosis at the knee: 1, medial compartment; 2, lateral compartment; 3, patellofemoral compartment.

Although osteoarthrosis at the knee is considered very common, its prevalence is overestimated. The reason is quite simple: radiographs taken in a middle-aged or elderly patients complaining of knee pain will always show some evidence of cartilaginous degeneration. As age advances, some narrowing of the joint space and osteophyte formation always appear; they are normal and cause no harm.¹⁶ Therefore the diagnosis of symptomatic osteoarthrosis should be made not by radiography but on the typical findings on clinical examination. A minor degree of osteoarthrosis does not give rise to symptoms and it is only when gross osteoarthrosis with disintegration of the cartilage supervenes that the complaints can be attributed to it. What commonly, but incorrectly, is labelled ‘osteoarthrosis’ is a monoarticular steroid-sensitive arthritis or an impacted loose body. Both occur in middle-aged or elderly patients with osteophytes showing radiologically, and the diagnosis is missed if full clinical examination is not carried out properly.

The symptom of osteoarthrosis is pain during weight bearing, which disappears at rest. In gross arthrosis with complete erosion of cartilage, nocturnal pain from an increase of venous pressure in the tibial bone may sometimes supervene.

The characteristic clinical features in uncomplicated osteoarthrosis of the knee joint are a cold joint, devoid of synovial thickening, with limitation of movement in the capsular pattern.

The end-feel is bony and hard. In severe osteoarthrosis, the marked limitation of movement in a capsular pattern is accompanied by loud creaking of bone against bone.

However, the typical capsular proportion of limitation may be absent if the osteoarthrosis, although severe, remains localized. This is often the case in localized arthrosis of the patellofemoral compartment: passive flexion may be markedly limited and painful but passive extension remains normal. In this case, the flexion–extension movement is accompanied by rough crepitus.

The treatment of osteoarthrosis is mainly with non-steroidal anti-inflammatory drugs (NSAIDs) and intra-articular injections with steroids. NSAIDs provide some relief of the symptoms but have clinically important side effects – they are estimated to cause 3300 deaths annually among the elderly in the US.¹⁷ Intra-articular injections with steroids also improve symptoms but the benefits are usually short-lived^18,19 and there is always the potential for long-term joint deteriorations if injections are repeated too often. During the last decade, a number of promising reports on the effect of intra-articular injections with hyaluronic acid have been published. Hyaluronic acid is an important component of healthy synovial fluid and cartilage tissue; it is thought to protect the articular cartilage and soft tissue surfaces of the knee by acting as a lubricant and, because of its high viscosity, by imparting viscoelastic properties to the joint. Because intra-articular hyaluronic acid concentrations are lower in the synovial fluid of arthrotic knees,²⁰ intra-articular injections with hyaluronic acid have been proposed as a means of restoring the viscoelastic properties of the knee joint, thereby providing symptom relief and improving joint function. Efficacy and safety of hyaluronic acid have been compared with that of saline,^21–23 corticosteroids²⁴ and NSAIDs. All the double-blind and randomized studies on the effect of hyaluronic acid on osteoarthrosis of the knee confirm that five intra-articular injections of sodium hyaluronate at weekly intervals are superior to placebo and are well tolerated in patients with osteoarthrosis of the knee, conferring a symptomatic benefit which persisted for 6 months.^25–27 As hyaluronic acid seems to provide beneficial effects with minimal adverse reactions in a significant number of patients, it may be considered as a substantive addition to the therapeutic armamentarium in osteoarthrosis.

When the condition is too advanced, joint replacement is the only solution.

Monoarticular steroid-sensitive arthritis

Cyriax described a monoarticular arthritis in the knee having some similarities with monoarticular arthritis in the shoulder and elbow. The cause and pathogenesis of this arthritis remain unclear but it heals immediately and lastingly after two injections of triamcinolone, thus earning it the title of ‘steroid-sensitive’ arthritis (Cyriax ²⁸: p. 404).

The patient describes a gradual onset of unprovoked swelling in one or both knees. At first, the swelling is completely painless. After some weeks or months, the knee starts to hurt all over. The pain is not provoked by movement and is often nocturnal.

In the initial stage, clinical examination shows only some diffuse warmth, fluid and synovial thickening. These marked symptoms and signs contrast strongly with the functional examination, which is almost completely normal. Only in advanced cases does a clear capsular pattern supervene.

Differential diagnosis

The differential diagnosis of a monoarticular steroid-sensitive arthritis, summarized in Table 52.1, must be made from the following conditions²⁹:

Table 52.1

Differential diagnosis of a capsular pattern at the knee

• Polyarthritis: in monoarticular steroid-sensitive arthritis, disease does not spread to other joints and the laboratory findings remain normal, distinguishing it from rheumatoid and reactive arthritis.30,31

• Villonodular arthritis of Jaffé and Lichtenstein³² is an advanced arthritis, with marked synovial hyperplasia and thickening of the capsule.³³ This type of arthritis is frequently complicated by spontaneous and recurrent haemarthrosis.^34,35 In doubtful cases, arthroscopic biopsy is indicated.³⁶ Treatment with steroid injections usually fails. Synovectomy is then advised.³⁷ Good results have also been reported with intra-articular injections of thiotepa.³⁸

• In middle age, a loose body complicating osteoarthrosis may be very difficult to distinguish. The distinct features of a loose body are sudden twinges, localized warmth and absence of synovial thickening. In long-standing arthritis, secondary wasting of the quadriceps muscle may make the knee feel weak and climbing stairs difficult; consequently, a complaint of twinges is not always a good sign. The only certain criterion may then be synovial thickening, which is not always ascertained easily, especially in middle-aged women, whose subcutaneous tissues are already somewhat thickened. In such circumstances, manipulation for a suspected loose body can be tried; if several attempts do not succeed, the joint should be injected.

• Gout and pseudogout have an acute onset with an immediate and gross articular pattern.

Treatment

The treatment of monoarticular steroid-sensitive arthritis at the knee is two injections of 40 mg of triamcinolone at an interval of 2 weeks (Fig. 52.4).

Fig 52.4 Intra-articular injection of the knee. Structures in (b): 1, patella; 2, suprapatellar pouch.

Technique: injection for monoarticular steroid-sensitive arthritis

The patient lies on the couch and relaxes the quadriceps muscle (Fig. 52.4a). If gross arthritis is present, it may be necessary to place a small cushion under the knee in order to keep it in slight flexion. The operator stands level with the other knee. With one hand the patella is pushed up and towards the operator, which makes the medial edge more prominent. A 5 mL syringe is filled with steroid suspension and fitted with a thin needle, 4 cm long, which is placed near the upper border of the patella and thrust in horizontally just between the patellar edge and the medial femoral condyle (Fig. 52.4b). It lies intra-articularly at about 2 cm depth.³⁹

Crystal synovitis

Gout

An acute arthritis at the knee occurs in 25% of all attacks of gout.⁴⁰ There is considerable pain, swelling and redness, which makes the condition difficult to differentiate from septic arthritis, haemarthrosis or pseudogout. Sometimes analysis of the joint fluid is necessary to distinguish these conditions.

Pseudogout

Calcium pyrophosphate crystals are believed to induce the synovitis of pseudogout. The term chondrocalcinosis refers to the presence of these calcium-containing salts in the articular cartilage,⁴¹ which are seen on radiographs.

The disease may be familial and is also commonly associated with a wide variety of metabolic disorders – for example, haemochromatosis, hyperparathyroidism, ochronosis and diabetes mellitus – and is also found in patients undergoing dialysis.42,43

As a rule, patients are over 60 years of age. Ninety percent of attacks of pseudogout are localized to the knees and there is an acute and recurrent arthritis which, untreated, lasts 1–4 weeks. Plain radiography may show calcification of the articular cartilage or menisci. Diagnosis is by aspiration, which demonstrates calcium pyrophosphate crystals in the fluid.

Pseudogout is best treated with an immediate intra-articular injection of triamcinolone. Alternatively, some of the oral anti-inflammatory agents can be prescribed.

Haemarthrosis

Villonodular synovitis

Haemarthrosis can occur in villonodular synovitis.52,53 Localized pigmented villonodular synovitis is a rare lesion that may affect any joint but is most often found in the knee. Treatment usually involves arthroscopic resection of the lesion.⁵⁴

Septic arthritis

Bacterial infection of the knee is an extremely serious disorder. If it is not properly treated, it will not only lead to total destruction of the joint but can also be life-threatening.

Septic arthritis can follow haematogenous dissemination from focal infections, such as urethritis, cystitis, skin infections ⁵⁵ or dental abscesses. This is particularly so when resistance is decreased: diabetes, rheumatoid arthritis, renal failure or a deficient immune system are all possible causes of decreased resistance.⁵⁶ Intravenous drugs and gonococcal infections, particularly with antibiotic-resistant gonococci,⁵⁷ have also been blamed for the increased incidence of septic arthritis of the knee. Another cause of septic arthritis is direct inoculation of organisms during intra-articular injection.

The symptoms of septic arthritis are hyperacute pain, swelling, redness and a gross articular pattern. The local symptoms are accompanied by high fever, chills and nausea.

Treatment is with high doses of antibiotics intravenously and daily aspiration of the knee.⁵⁸

Non-capsular pattern

Internal derangement

Introduction

Impaction of loose tissue within the joint cavity, causing mechanical interference with the normal movement between femur and tibia, is usually referred to as ‘internal derangement of the knee’. The loose tissue consists of meniscal parts, cartilaginous tissue peeled off from meniscus, joint cartilage or bony fragments, as is the case in osteochondritis dissecans.

Symptoms and signs in internal derangement are quite typical. The pain is localized, of the mechanical type and has a sudden onset. ‘Locking of the joint’ and ‘twinges’ are typical sensations. The former describes sudden and painful limitation of one movement; the latter is abrupt, unforeseen and sharp pain that appears during weight bearing.

The clinical signs are a non-capsular pattern and a typical bouncing or springy end-feel. The latter is typically found during passive extension.

A thorough clinical assessment can usually provide sufficient information to make a definitive diagnosis of internal derangement.⁵⁹ Plain radiographs are of no use in the diagnosis of internal derangement. Arthroscopy may be useful but should never be performed without first completing a full preoperative examination.

Lesions of the meniscus

These can be grouped into congenital anomalies, traumatic conditions, cysts and metabolic disorders.

Congenital anomalies

The most common congenital anomaly with pathological sequelae is a discoid lateral meniscus. The incidence in autopsy specimens is between 0% and 7%,⁶⁰ but most do not cause problems.⁶¹ Symptomatic disorder seems to occur only in the Wrisberg ligament type of discoid meniscus. This type is classically described as lacking a posterior capsular attachment and presents in childhood with a ‘snapping’ knee: the meniscus rolls up in front of the lateral compartment during flexion, as a consequence of increased friction and greater mobility; during extension, the rolled meniscus becomes trapped anteriorly, until it reduces suddenly with a dramatic audible snap (Fig. 52.5).⁶²

Fig 52.5 Discoid lateral meniscus: the meniscus which rolls up in flexion (a) is trapped during extension (b) until it reduces with a ‘snap’, allowing full extension (c).

The disorder affects children and adolescents. The presenting symptom is internal derangement at the lateral side of the knee. Clinical examination reveals an audible click and visible alteration of the knee at approximately 10–20° of extension.⁶³ Diagnosis is confirmed with sonography or magnetic resonance imaging (MRI).⁶⁴

Treatment of a congenital discoid meniscus is complete or partial meniscectomy.⁶⁵

Traumatic meniscal lesions

Disruption of collagen fibres within the meniscus occurs as the result of either an acute injury or gradual age-dependent degeneration (Fig. 52.6). The split may be either horizontal or vertical.

Fig 52.6 Main types of meniscal tear: 1, horizontal; 2, longitudinal; 3, radial; 4, degenerative; 5, flap.

Vertical tears

Vertical tears are the most important clinicopathological condition of the meniscus and usually result from excessive force applied to a normal meniscus. Transverse tears are less common than longitudinal ones. The latter frequently involve the thin inner edge of the meniscus, which, when it separates, creates the bucket-handle tear, so characteristic of the locking knee.⁶⁶ Peripheral longitudinal tears are defined as those occurring within 3 mm of the meniscosynovial junction and comprise about 30% of all vertical tears.⁶⁷ Left untreated, most of these peripheral lesions heal spontaneously.⁶⁸

The less mobile medial meniscus is much more commonly involved than the lateral meniscus. The medial meniscus is closely bound to the medial collateral ligament and the medial coronary ligament, which attaches the meniscus to the tibia, is only 4–5 mm long. The lateral meniscus, however, is separated from the lateral collateral ligament by the popliteus tendon, and its coronary ligament is much longer (13–20 mm).⁸ This difference in mobility is the reason for the higher proportion of torn medial menisci.

The typical vertically torn meniscus, which results in a bucket-handle lesion, occurs between the ages of 15 and 30 years. The mechanism of injury is as follows: during flexion–extension, the menisci move with the tibia, to which they are attached (see online chapter Applied anatomy of the knee), but during rotational movements they follow the femoral condyles. During combined movements, the normal displacement of both menisci may be prevented and the menisci become trapped between tibia and femur. This typically happens in a football player who, in an attempt to kick the ball sideways, severely twists on the slightly flexed and weight-bearing knee: the rotation force of the femur on the immobilized tibia then ruptures the cartilage. It has also been suggested that meniscal lesions may appear as the result of knee instability, in particular after anterior cruciate lesions.^69,70

The typical history of a bucket-handle lesion is that of a patient, usually a male soccer player aged between 16 and 30 years, who felt agonizing and localized pain, usually at the inner side of the knee, during a vigorous rotation with weight bearing. The knee gave way and the patient fell to the ground. When he stood up again, the knee could not be straightened; although it could be bent, it was impossible to force it into extension. Full extension was only regained when either the patient, the trainer or the doctor forced the knee to unlock by a combined rotational and extension movement. After an audible click, full extension immediately became possible again. After reduction, the knee became swollen and sore for a couple of days. After a week or two, the patient may then find the knee is ‘cured’, providing it is not twisted while weight bearing. Should that happen, something painfully ‘going out’ in the joint would be felt and, as before, straightening the joint would not be possible. Again, the limitation of movement disappears only if the knee is manipulated.

The biomechanical basis for the locking is that, in a normal knee, the collateral ligaments and the posterior aspect of the joint capsule all become taut during extension. When the slack in the ligaments has been taken up, the tibia and femur are strongly approximated and extension beyond 180° is prevented. At full extension, there is no room for a displaced piece of cartilage between the two bones and therefore the movement must be somewhat limited by its presence. Sudden locking of the knee in partial flexion, with immediate unlocking on manipulation, is therefore pathognomonic of a bucket-handle tear.

Horizontal and posterior cracks

It is generally accepted that these lesions result from normal forces acting on a degenerating meniscus.⁷¹ Degenerative horizontal cleavage lesions are therefore more common in individuals of more than 40 years of age and usually occupy the posterior half of the menisci.^72,73 They are so common that most authors regard them as part of the usual degenerative processes in the knee (Noble and Turner,⁷⁴ Fahmy et al,⁷⁵ Smillie⁹: pp. 79, 97, 108, 145, 153).

In a posterior crack, the history is less dramatic than in that of a vertical tear.⁷² For instance, the patient finds that, if there is a twist on the knee, something is occasionally felt to ‘give way’, usually at the back of the joint. It is immediately difficult to straighten the leg, but when it is shaken or kicked out, a click is heard and the limb returns to normal function. Sometimes the patient gives a different history: slight rotation and flexion during weight bearing – for example, on getting out of a car – produce an uncomfortable click which is relieved immediately on straightening the leg.

Diagnosis

Ruptures with displacement

In a longitudinal vertical tear, the history is most informative: the patient states that on twisting the leg during weight bearing a click is heard, localized unilateral pain is felt and the knee immediately locked in flexion. All unassisted attempts to straighten the knee fail.

The patient enters the room with a characteristic gait: hopping on one leg with the knee on the affected side flexed and the foot plantiflexed with the toes just touching the ground.

Clinical examination reveals a warm and slightly swollen joint. Flexion is normal or somewhat limited by the traumatic arthritis but when extension is attempted, limitation of 5–10°, with a characteristic springy block, is detectable. Rotation away from but not towards the affected side is painful.

Palpation usually reveals a very tender joint line at the affected side, because of a coincident sprain of the coronary ligament.

When a middle-aged patient presents with a posterior displacement, extension may be just possible but very painful, and once again the end-feel of a springy block is informative. In this type of lesion, tenderness is not found on palpation.

In a horizontal lesion, a visible and palpable ‘tag’ can form, which then projects at the joint line. Often digital pressure will suffice for reduction but this is seldom permanent.

Ruptures without displacement

If the patient is seen some time after reduction of the meniscus, the knee may appear normal or merely shows a sprained coronary ligament. Alternatively, the patient presents with a history of a minor posterior crack but the routine functional examination is normal. In these cases, the following tests can be used to elicit signs of a ruptured meniscus (Fig. 52.7).

Fig 52.7 (a) Test 1: to detect clicks during rotation in full flexion. (b) Test 2: to detect a click during extension movement under external rotation. (c) Test 3: palpation of a displaced rim.

Test 1.

The knee is fully flexed. The examiner holds the index finger and thumb at both sides of the patient’s infrapatellar tendon, level with the joint line. With the other hand, the heel is grasped and the leg rotated quickly to and fro. When clicks are felt at the joint line, a ruptured meniscus should be suspected.

Test 2.

The knee is fully flexed and rotated. One hand is placed on the knee, the index finger at the side to be tested and level with the joint line. The examiner now slowly extends the patient’s knee, while the pressure maintaining rotation is maintained. As extension proceeds, a click indicating a meniscal tear may be felt, usually as the leg approaches the neutral position at almost full extension. This test can also be performed during varus or valgus compression and is then called the McMurray test.

Test 3.

The knee is held well flexed. The examiner passes the flexed thumbtip from above downwards over the joint line at the affected side. A ruptured meniscus should be suspected when it is possible to hook the rim of the meniscus and pull it downwards until it jumps back into place again. Normally this is accompanied by an audible click.

Test 4.

Medial and lateral shearing strain has been discussed in the chapter on clinical examination (p. 670–671). The knee is flexed at a right angle. The examiner sits at the foot of the couch and interlocks the fingers on the patient’s knee. A strong shearing strain can now be exerted to move the tibia laterally or medially on the femur. This manœuvre may elicit pain or even displace the loose part of the meniscus to the other side of the condyle. A loud click is heard, with immediate loss of full passive extension. A torn meniscus is obvious, in that the test has provoked a subluxation. Manipulative reduction must follow, of course.

Test 5.

If there is a horizontal split, a ‘tag’ of cartilage can be felt to protrude at the joint line, and can be pushed back into place by the palpating finger. The discomfort on full extension then immediately ceases but recurrences are common. If this is the case, the patient can learn to perform the ‘manipulation’ themselves.

Arthroscopy

During recent decades, arthroscopy has made the diagnosis and treatment of a torn meniscus much easier.76,77 Nevertheless, arthroscopy does not make a clinical diagnosis redundant and routine arthroscopy without a previous thorough functional examination can lead to wrong conclusions and treatment. Because meniscal lesions are so common that they are a frequent finding in middle-aged people, it is very possible that a meniscal tear, found incidentally during ‘routine’ arthroscopy, is not the cause of the patient’s complaints. For instance, if a patient with a chronic ligamentous lesion of the medial collateral band or the coronary ligaments is subjected to arthroscopy before a clinical diagnosis has been made, the damaged meniscus will be blamed and thus unnecessarily removed.

The use of the arthroscope has encouraged the widespread assumption that the source of chronic pain in the area of the knee is to be found in the interior of the joint itself. The more likely cause of pain, however, is in the surrounding ligaments, but this can only be demonstrated by a thorough clinical assessment.⁷⁸ We, like Goodfellow (‘He who hesitates is saved’),⁷⁹ believe that, although meniscal tears can be detected by arthroscopy with almost 100% accuracy, caution is needed in ascribing symptoms at the knee to meniscal lesions. Diagnosis of meniscal lesions should be made clinically and arthroscopy should be reserved for confirmation of clinical findings as an aid in therapeutic decision making.

Treatment

Manipulative reduction

Manipulation should be tried at once in a patient who presents with a displaced meniscus. The manipulation is not completely painless and anaesthesia may sometimes be required, especially if the patient is tense or anxious. Although some authors advise general anaesthesia, sufficient pain relief can be obtained after an intra-articular injection of 5 mL of lidocaine 2%.

Technique: starting position.

The patient lies supine on the couch and flexes the hip and knee to right angles. Every effort must be made to encourage the patient to relax the muscles as much as possible.

In a displaced medial meniscus, the manipulator must open up the inner aspect of the knee as far as possible. Therefore, strong valgus pressure must be exerted during the whole procedure. In order to achieve this, one hand is placed at the outer side of the knee, so that the thumb lies at the back of the knee. This thumb position is important in controlling extension during the preparatory phase of the manipulation. The other hand encircles the heel to rotate the leg to and fro during the manipulation.

Technique: preparative phase.

The hip is slightly rotated medially and strong valgus pressure is exerted at the knee (Fig. 52.8). In this position, repeated extensions are performed but not beyond the end of range – i.e. if the extension range is limited by 10°, the movement should stop at about 15°. In order to ensure this, the thumb placed in the popliteal fossa is used as a brake during the procedure. Once flexion and extension movements have been performed several times in this way, rapid to-and-fro rotations of the knee are added.

Fig 52.8 Manipulative reduction of a displaced medial meniscus.

Technique: manipulation.

The movements are now performed rapidly and repeatedly. When the patient is most relaxed, one quick thrust towards further extension is added. This is achieved by strong, swift, downward and inward pressure of the hand at the knee joint at the end of the extension. As the full range of extension is reached, reduction is signalled by a small click, at which point extension at the knee immediately becomes free.

If symptoms of a sprained coronary ligament persist after successful manipulation, deep transverse friction should also be applied. Further splinting or immobilization, in order to heal the tear, is of no use.

Natural history

The meniscal lesion itself causes no pain because the body of the meniscus is almost completely insensitive. Pain is the result of ligamentous strain caused by the repeated luxations and subluxations. However, damaged menisci frequently do not provoke any symptoms. In a postmortem study in patients above and below the age of 50, Noble and Hambden found that up to 60% of the former and 19% of the latter had meniscal tears.80,81

It is important to realize that most complaints following subluxation of a meniscus stem from a sprained coronary ligament. If a patient with a history of a former locked meniscus complains of persistent and localized pain but proves to have a full range of movement with a normal end-feel, a sprained coronary ligament should be suspected and appropriate treatment given. After successful manipulation, the reduced piece of cartilage may never subluxate again and the patient is cured for good. This was emphasized by Casscells,⁸² who stated that not all meniscal tears need surgical treatment. Asymptomatic meniscal tears identified at the time of arthroscopic examination for ligamentous lesions are best left in place or unrepaired, as they will remain asymptomatic.⁸³ Furthermore, laboratory studies have demonstrated that torn menisci may have normal biomechanical function if the peripheral circumferential fibres remain intact.^84,85

Surgery

Although surgery of the meniscus should not be undertaken lightly, it is unwise to permit repeated attacks of internal derangement because they initiate a premature, troublesome and intractable osteoarthrosis.75,86

The choice lies, then, between total or partial meniscectomy or repair. Total meniscectomy leads to loss of integrity of the articular cartilage and impairment of joint stability.87–91 It is no longer considered the treatment of choice because of increasing dissatisfaction with the long-term results.^10,92 Instead, and if this is technically possible, only the loose fragment is removed and the outer part of the meniscus, together with the coronary ligament, is left alone.⁹³ The result is no increase in weight-bearing stress on the tibia.⁹⁴ The outer rim of the meniscus can still bear weight and thus preserve the articular cartilage, as well as play a useful role in stabilizing the joint. In experienced hands, this partial removal of the meniscus using arthroscopy is much less damaging to the joint and requires only 2 days’ bed rest. Subsequent return to work and sport is also quicker.⁹⁵ Several long-term studies have demonstrated the technique’s superiority over total meniscectomy.^96–100

In recent years, suturing of the relatively vascular outer edge of the meniscus has been shown to result in healing by fibrous tissue.101–107 Meniscal repair is nowadays considered as the treatment of choice in single, vertical, longitudinal tears in the outer third of the meniscal substance.¹⁰⁸ Good to very good long-term results may be expected if the longitudinal tear is less than 3 cm long and within 3 mm of the periphery, and the meniscal tissue is not degenerating.^109,110 Ligamentous instability is a relative contraindication to repair. In combination with insufficiency of the anterior cruciate ligament, the rate of retearing approaches 40% and therefore anterior cruciate ligament reconstruction should be performed at the same surgical intervention.^111,112

Cysts of the meniscus

When cysts form, they are almost always at the lateral meniscus; a cyst of the medial meniscus is extremely rare.¹¹³ There is evidently a connection between cyst formation and the existence of ruptured menisci because half the cystic menisci are also torn.¹¹⁴

The history can be indicative of internal derangement or the patient may complain of localized pain when standing for some time.

Clinical examination reveals a normal range of movement and a normal end-feel. Ligamentous tests are negative. When the joint line is palpated during full extension, the cyst is felt there as a small firm mass that varies in apparent size depending on the position of the knee, usually being most prominent in 20–30° of flexion and disappearing on full flexion (Pisani’s ‘disappearing’ sign).¹¹⁵ Some tenderness is elicited at the joint line and over the cyst. The diagnosis can be confirmed with MRI.¹¹⁶

Treatment is aspiration of the cyst. It is important to use a large-bore needle and to insert it in several different directions, as the cyst is often multilocular.¹¹⁷ Arthroscopic treatment is used if the cyst recurs.^118–120

Metabolic disorders affecting the meniscus

The most important metabolic condition affecting the menisci is chondrocalcinosis. A recent random autopsy study found calcium pyrophosphate dihydrate crystals in 7% of the menisci examined.¹²¹ Chondrocalcinosis of the meniscus is considered in the previous section of this chapter (‘Capsular pattern’).

Loose body in young patients

Loose bodies, which are often multiple, can form in the knee in teenagers and young adults. They are usually the result of osteochondritis dissecans but sometimes originate from chondromalacia patellae or a small osteochondral chip fracture.

Osteochondritis dissecans is well known, although the true cause is still not completely understood. In those under the age of 13 years, the condition seems to result from an abnormality of ossification. In teenagers and adults, however, trauma may have a significant part to play in the development of the lesion.122,123 More than 75% of the osteochondral lesions are on the lateral side of the medial femoral condyle.¹²⁴ About 10–15% are situated at the lateral femoral condyle and in less than 10% of the patients the lesions are bilateral.¹²⁵

Few symptoms result, as long as the osteochondral lesion remains stable and embedded in the condyle (Fig. 52.9). There is some vague pain during weight bearing which can also be elicited during pressure over the medial condyle. Symptoms of intermittent pain and locking of the joint occur only when the fragment has become loose, which typically happens between 16 and 20 years of age.

Fig 52.9 Stable osteochondral lesion (a) and loose fragment (b) at the lateral aspect of the medial femoral condyle of the left knee (interior view).

The history is of a sudden and temporary locking in extension. The patient finds that, from time to time while walking along, the knee suddenly locks. If this happens while doing sports, a fall to the ground is usual because the knee is locked straight when the patient expects to be able to bend it. When flexion is attempted again, this is successful and walking on it is immediately possible. Some aching and traumatic arthritis result for the next few days. Recurrence of this sequence is common and the location of the pain may vary, indicating that the loose body has shifted to another part of the joint.

After the attack of internal derangement, there are signs of a traumatic arthritis only: the knee is warm, contains some fluid and shows a slight capsular pattern. The ligamentous tests are normal and there is no local tenderness. Sometimes the loose body can be felt in the suprapatellar pouch. Wilson ¹²⁶ describes a test that aids in the diagnosis. The knee is flexed to a right angle and the tibia rotated internally; the examiner then slowly extends the patient’s knee. At about 30° of extension, pain may occur, presumably arising from the lesion at the inner condyle pressing against the tibial spine.

Loose bodies have an osseous nucleus and therefore can be seen on a radiograph. In true osteochondritis dissecans, the gap at the lateral side of the medial femoral condyle is also seen on an anteroposterior and a tunnel view.

Stable osteochondritis dissecans has a successful healing rate of 50% after 6 months of relative rest.¹²⁷ However, because the chance of spontaneous healing is low for juvenile osteochondritis dissecans lesions that present with disruption of the articular cartilage surface, and the risk of further damage is high, most surgeons recommend surgical stabilization of all unstable juvenile osteochondritis dissecans lesions at the time of presentation.¹²⁸ The method used depends on the size of the defect and the congruity of the fragment with its bed. Sometimes replacement is tried, and sometimes removal of the loose fragments by arthroscope.¹²⁹

The differential diagnosis and treatment of loose body and meniscal tear in a young patient are summarized in Table 52.2.

Table 52.2

Differential diagnosis and treatment of loose body and meniscal tear in a young patient

Loose body complicating osteoarthrosis

Cyriax ²⁸ (his p. 403) pointed out that:

When a middle-aged or an elderly patient presents with signs of a ligamentous sprain, or a traumatic arthritis, and there has been no injury, it is highly probable that he suffers from a loose body.

Contrary to popular belief, minor or moderate osteoarthritis at the knee does not cause symptoms.¹³⁰ However, if there is some crepitating osteoarthritis, the articular cartilage is roughened. A small piece may then exfoliate. Alternatively, a small piece of degenerated meniscal cartilage may peel off and escape into the joint space. Such a loose fragment can occupy a harmless position at the back of the joint, or in the suprapatellar pouch, but sometimes impacts between the articular surfaces, where it occupies space, induces overstretching of the ligaments and causes localized pain.

History

The history of a loose body is typical. The patient is middle-aged or elderly and states that, for no reason, swelling and localized pain appeared in one knee, usually at the medial side. Pain may be present on waking or suddenly each step hurts when walking. Sometimes pain is felt at the lateral side, or right in the joint, but never all over the joint. Curiously, the pain can sometimes spread up to the distal part of the thigh or down to the proximal part of the leg. If the pain moves from one side of the joint to the other, the diagnosis is obvious because moving pain suggests a moving (and free-lying) lesion.

The patient is hesitant to go downstairs for fear of a sudden twinge which makes the knee give way. Therefore descent is usually one step at a time, firmly holding on to the banister. Less often, the twinges and the feeling of instability are experienced during ordinary walking. Twinges indicate a momentary impaction in the knee joint and in middle-aged people they are almost pathognomonic of the existence of a loose body.

Sometimes pain also occurs at night; this is likely to happen when it is at the medial side of the knee. One possible explanation could be local tenderness at the medial collateral ligament when the knees are held together while the patient lies on the side.

Clinical examination

The signs vary with the position of the loose fragment within the joint but there are some that are always present and draw attention to the condition:

• Localized warmth: There is localized warmth on the painful side of the joint. If the joint is not warm at the beginning of the clinical examination, the examiner proceeds with the functional tests and repeats the palpation at the end. Local heat is then found which has been provoked by the minor stresses imposed on the joint during examination.

• Fluid: often, some fluid is present.

• Non-capsular pattern: there is usually a non-capsular pattern. It is obvious that when extension is limited by, e.g. 5° and flexion is not, or flexion is 30° limited but extension is of full range, a block due to internal derangement should be suspected. Such an obvious non-capsular pattern is rather uncommon and, as a rule, the signs are quite subtle. Extension is full but painful and has a smoother end-feel than on the opposite side, while flexion is full and painless. Alternatively, full extension is free from pain but flexion is slightly limited, with localized pain and a soft end-feel. In other words, the stop is not hard, as if muscle spasm due to arthritis was present, but feels as if it would go further, the limiting factor being pain.

• A varus movement hurts at the inner side of the joint: this indicates that a space-occupying lesion is present in the medial compartment. Alternatively, lateral or medial shearing strain may hurt at the inner or the outer side of the joint. Care should be taken not to press on the tender medial collateral ligament during these tests.

• Localized pain and positive ligamentous tests: there is localized pain at the end of range and some ligamentous tests are positive. As a rule, valgus strain and external rotation hurt at the medial side. The medial collateral ligament is also very tender to the touch. Usually these findings, together with localized warmth, fluid and absence of synovial thickening, are characteristic of a sprained ligament. However, the patient does not mention trauma. The conclusion is that, if the ligament is not being strained by external forces, the cause of the sprain must lie within the joint: the ligament becomes sprained when a small cartilaginous loose body is displaced between femoral condyle and tibial plateau, where it will put stress on the ligaments on every attempt to extend the joint. Cyriax called this ‘a sprain without a sprain’.

If, after the clinical examination, the conclusion is that there is an impacted loose body, an attempt should be made to move the piece of cartilage to a site where it no longer interferes with joint mobility. Confirmation that the diagnosis is correct comes from the immediate disappearance of symptoms and signs after manipulation.

Special investigations

The knees of elderly patients always show radiological evidence of osteoarthrosis. Loose bodies, however, usually being composed entirely of cartilage, are not visible on radiography. When the radiograph shows osteoarthritis, the current tendency to depend on diagnosis by such means rather than by good clinical assessment can result in the clinical features being ignored and the patient being erroneously regarded as suffering from osteoarthrosis of the knee. The acute onset and the warmth are then mistakenly labelled as ‘acute episodes’ of progressing osteoarthrosis.

It is also apparently very difficult to see small loose bodies during diagnostic arthroscopy. It is striking, however, to hear that surgeons often see an improvement of symptoms and signs in an ‘arthrotic’ knee after such a procedure.131–133 In all likelihood, the loose bodies are washed out inadvertently during the drainage that is necessary for arthroscopic investigation and it is a consequence of this that the patient notices an improvement.

Differential diagnosis (Table 52.3)

Spontaneous osteonecrosis of the knee occurs in elderly patients, usually at the medial femoral condyle.¹² The condition causes continuous pain which gets worse at night, but twinges are not mentioned. Clinical and radiological examinations are negative during the first few weeks of the condition’s development,^134–136 and early diagnosis must be made by a bone scan^137,138 or by the use of MRI. The treatment is proximal osteotomy or prosthetic replacement.¹³⁹

Table 52.3

Differential diagnosis and treatment of an impacted loose body complicating arthrosis at the knee

The most common error, however, is to regard the patient with a loose body as suffering from osteoarthrosis or a monoarticular steroid-sensitive arthritis. Because all these lesions occur in middle age or in the elderly and the signs are sometimes subtle, the distinction is not always apparent. In case of doubt, it is always wise to manipulate the knee and see whether there is any improvement.

Treatment

As soon as impaction of a loose body in a knee is diagnosed, manipulation must be performed. The intention behind the manipulation is to move the loose body from its position between the tibial and femoral articular surfaces into a position in the joint where it is no longer pinched, i.e. under the posterior recess. To make room between the tibia and femur, the whole procedure is performed during strong traction.

First manipulation

The principles of performing a manipulation for a loose body are:

• Traction should be as strong as possible.

• The manipulation starts with the ligaments in a relaxed position (knee in flexion).

• During movement towards extension, the knee is rotated three or four times, first in one direction and then, if no improvement results, in the other.

Technique: starting position

The patient lies prone on a low couch, the knee flexed to a right angle. An assistant holds the thigh just above the popliteal fossa. The manipulator stands level with the patient’s knee. The ipsilateral hand grasps the calcaneus. The other hand is placed at the dorsum of the foot in such a way that the second metacarpal bone presses against the neck of the talus (Fig. 52.10a). The pressure against the talus and the simultaneous traction on the calcaneus hold the foot in dorsiflexion during the whole procedure (Fig. 52.10b).

Fig 52.10 First manipulation for a loose body impacted in the knee.

The manipulator places the contralateral foot on the couch, just in front of the patient’s knee. The patient’s thigh is lifted off the couch and the foot is hooked on the manipulator’s knee. The assistant now presses the thigh downwards as hard as feasible. This ensures maximal traction on the relaxed ligaments and creates some distraction of the joint surfaces. This position is maintained for a few seconds until the manipulator feels the quadriceps muscle relax, and the tibia is distracted from the femur.

Technique: manipulation

The manipulator now removes the leg from the couch and, leaning sideways towards the end of the couch, places the foot as distally (in relation to the patient) as possible (Fig. 52.10c). By doing so, maximum traction is ensured during the whole procedure. Extension is accompanied by a series of full lateral or medial rotations (Fig 52.10d). To this end, both shoulders and elbows must be used in order to reach the very end of rotation. The end-feel will once again be a guide in deciding whether the knee is at full range. In practice, rotation is tried first in one direction and then, if this does not succeed, in the other. The assistant who is holding the leg down feels a click, indicating that reduction has taken place, but the manipulator does not feel anything. After each manipulation, whether the knee has clicked or not, the joint is examined again. If there is improvement after a particular manœuvre, the same manipulation is done again.

Results

If the manipulation only reduces an impacted loose body incompletely, then other techniques must be tried.

This manipulation is painless and can be repeated up to 10–20 times during one session. Usually one or two sessions suffice for full relief, even if the condition has been present for months.

Second manipulation

If the previous manœuvre has only partially improved flexion but has not completely reduced the loose body, techniques that use leverage can be employed next. If the wrist is placed at the back of the patient’s knee, forced flexion of the tibia on the femur will strongly distract the joint surfaces and thus make room for the loose fragment to move.

Technique

The patient lies supine on the couch. The manipulator places one wrist in the popliteal fossa, between tibia and femur, while the other hand presses at the distal end of the tibia. The knee is then bent as far as it will go (Fig. 52.11a). When progressive ligamentous resistance indicates that the slack has been taken up, the tibia is quickly forced into greater flexion with a small thrust. A click may be felt. Re-examination will show whether further reduction has taken place.

Fig 52.11 Second manipulation for a loose body impacted in the knee: two alternative methods are shown.

If this manipulation fails, the same movement can be repeated during rotation . The manipulator places a firm rolled bandage in the popliteal fossa (Fig. 52.11b). This permits the patient’s foot and wrist to be held with both hands. Rotational movements can be added during the forced flexion. First one rotation is tried; should this fail, rotation in the opposite direction is attempted.

It is important to verify the range of extension after each attempt, because full and painless extension at the knee is more important than some improvement of flexion. Should the range of flexion improve but extension become painful or limited, this manipulation should be terminated immediately.

Third manipulation

This technique is used when the first manipulation does not achieve full and painless extension. In most cases, extension is not limited but is painful and has an altered end-feel.

Technique

The patient lies supine. The manipulator stands level with the knee, and bends it to a right angle while the hip is flexed and laterally rotated. The hand is applied at the inner side of the knee and the other hand at the lateral border of the distal tibia in such a way that a strong varus movement is achieved (Fig. 52.12).

Fig 52.12 Third manipulation for a loose body impacted in the knee.

The patient’s cooperation is now sought because the knee must be actively and slowly extended while the manipulator maintains the varus pressure. At almost full extension, and maintaining as much varus pressure as possible, the manipulator adds a quick jerk towards full extension. If this final jerk proves to be too painful, it should only be done a few times, after repeated active extension by the patient.

Once again, re-examination should follow each attempt and the end-feel will indicate whether reduction has taken place (Fig. 52.13).

Fig 52.13 Manipulative session for a loose body.

Instructions on after-treatment

During the following days the patient must repeat the manipulation several times a day. To do this, the patient sits on a low chair or on the ground, the knee flexed and the hip laterally rotated. The lateral border of the foot now rests on the floor. Pressing strongly on the inner side of the knee, and at the same time actively extending the leg, results in a varus movement during active extension (Fig. 52.14). Fixation of the lateral border of the foot against the floor ensures the counterpressure needed for a good varus stress. At nearly full extension, a small thrust is added.

Fig 52.14 After-treatment exercise by the patient.

Results

Most impacted loose bodies complicating osteoarthrosis are reduced by one or two manipulative sessions. No after-treatment to the strained ligaments or the slight traumatic arthritis is necessary, because they will recover within a few days without specific treatment. Recurrences of the impaction are always possible, mainly after kneeling or keeping the knee bent for some time. Patients should therefore be told not to squat or to sit sideways on a couch with the legs tucked underneath, a sitting position often adopted by women.

Plica synovialis syndrome

Plicae synoviales are remnants of the embryological dividing walls in the knee. Arthroscopy has recently brought their existence to prominence. They are present in more than 20% of all knees,¹⁴⁰ but it is only when pathological changes take place that pain and disability are likely to occur. Injuries and excessive strains are thought to be responsible for these pathological alterations.^141,142

Although there are several types of synovial plicae, it is the plica mediopatellaris, or medial shelf (Fig. 52.15), which seems to cause most problems.¹⁴³

Fig 52.15 Medial plica (1).

This plica was first described by Iino in 1939.¹⁴⁴ It has its origin on the medial wall of the knee joint and runs obliquely down towards the synovium, inserting into it and covering the medial infrapatellar fat pad. During flexion it glides over the medial condyle like a wiper over a windscreen, which in normal circumstances is harmless and painless; if the plica is pathologically altered or the medial condyle has undergone arthrotic changes, however, symptoms may result.

One of these symptoms is a sudden twinge when the inflamed plica is pinched between the patella and the medial condyle of the femur. Sometimes there is pain and a slightly modified end-feel at the end of extension. A painful arc during flexion–extension can occur when a damaged and thickened plica rides over a chondral defect at the medial condyle, and it can be aggravated when this movement is performed during lateral rotation.145,146

The clinical diagnosis of a symptomatic medial plica is made from a history of localized pain during flexion–extension or pain at the end of extension.¹⁴⁷ The plica can sometimes be felt if the examiner rolls the medial capsule of a slightly (45°) flexed knee under the thumb.¹⁴⁸ When this rolling is painful, 20 mg of triamcinolone is locally infiltrated.^149,150 Some authors have reported good to fair results with flexibility training of the flexor and extensor muscles of the knee.^150,151 If the symptoms persist, arthroscopic resection is performed.¹⁵²

Because the presence of a medial shelf is normal,¹⁵³ one should be cautious in ascribing symptoms to it. The diagnosis should be made clinically and not by relying on accidental findings during arthroscopy.

Intra-articular adhesions

There is an unusual disorder of the knee, characterized by an increasing limitation of flexion while extension remains full and painless. As this pattern occurs after operation or an unexceptional sprain, Cyriax ascribed it to intra-articular adhesions.

The history is as follows. There has been surgery to the medial side of the knee or an atypical sprain (hyperextension or hyperflexion) that has given rise to the lesion. In spite of vigorous physiotherapy, the knee stiffens progressively and almost painlessly, the main symptom being inability to flex the joint. During the initial weeks, 15–30° of flexion are lost; after a month there is loss of about 90° of flexion. While the range of flexion decreases day by day, extension remains full and painless. Finally, the knee may stiffen with a flexion range of 45°, extension still being full-range.

Clinical examination immediately reveals the gross non-capsular pattern. Furthermore, the joint is cold but not swollen; nor is there any capsular thickening. The combination of the non-capsular pattern, gross limitation of flexion and absence of local signs is so striking that this remarkable condition will be recognized easily, especially if there is a history of trauma or surgery.

The only lesion that can be confused with these intra-articular adhesions is Stieda–Pellegrini disease, in which the calcified medial collateral ligament can cause a similar selective limitation of flexion. A radiograph establishes the diagnosis.

Treatment

Gentle forcing does not prevent the progressive decrease of flexion and any conservative treatment, except forceful manipulation towards flexion, is futile. It is easiest to force the knee when the patient adopts a prone position.

Technique

The manipulator stands at the level of the knee, which is bent as far as possible. The elbow is curved around the distal aspect of the tibia. The other forearm is placed at the back of the knee, just above the popliteal fossa. The hands are locked. Flexion is now performed by a side bending of the body towards the patient’s head. A great deal of force can be obtained if the manipulator keeps the arms still. The arm on the thigh keeps the knee on the couch, while the other arm uses the tibia as a lever. The manipulation is executed during a quick side bending of the whole body, with as much force as possible. Often a loud sound of ripping, tense tissue can be heard; flexion can be achieved immediately, thus proving that there were adhesions.

Follow-up

Within 24 hours, there is considerably more pain than before the manipulation and the patient has symptoms of significant arthritis: a warm joint, full of fluid and demonstrating an articular pattern. During the following days, active and passive exercises are prescribed in order to maintain the range of flexion. When arthritis is gross and pain severe, an intra-articular injection with 50 mg of triamcinolone can be given in order to diminish the traumatic capsulitis.

Subsynovial haematoma

A severe blow on the front of the thigh may cause a localized haematoma between the suprapatellar pouch and the front of the femur (Fig. 52.16). Flexion is limited but extension remains free.

Fig 52.16 Subsynovial haematoma (1).

The history is typical: a severe knock just above the patella has caused immediate pain and localized swelling.

During clinical examination, the knee is found to be warm and swollen. Extension is full but probably painful at the end of its range. Passive flexion is grossly limited and there is localized pain just above the patella. Resisted extension is painless, which indicates that neither the quadriceps tendon nor the patella is to blame. Palpation reveals some fluid in the joint and a solid, tender swelling at the suprapatellar pouch.

Fluid aspirated from the joint is clear or slightly blood-stained. There is no improvement in range after aspiration, which establishes that the effusion is a secondary one. If the needle is passed just above the patella, in the direction of the femur, blood from the haematoma can be obtained and confirms the diagnosis. It is important to note that aspiration is possible only during the initial few days because the haematoma organizes rapidly.

After aspiration, the knee should be mobilized during the following days in order to prevent persistent adhesions.

Adherent vastus intermedius

The vastus intermedius may become adherent to the femur after a fracture of the latter. Gross limitation of flexion then results. Only surgical treatment gives a satisfactory outcome.

Posterior capsular strain

There is a history of a severe hyperextension strain. When traumatic arthritis has subsided and flexion becomes full and painless, extension continues to hurt at the back of the knee. The rest of the clinical examination shows the knee to be normal and therefore strains of anterior or posterior cruciate ligaments are excluded. In long-standing cases, an X-ray may show the typical appearance of slight calcification in the posterior capsule.

Treatment consists of infiltration with triamcinolone at the appropriate side, using the same technique as for posterior strains of the posterior cruciate ligament (see p. 709).

Cysts and bursitis

It is important to note that localized swellings may limit movements in a non-capsular way (Fig. 52.17). For example, a bursa underlying the medial collateral ligament, a prepatellar bursa or a cyst under the iliotibial tract can each cause a specific pattern.

Fig 52.17 Cysts and bursitis around the knee: 1, patellar bursitis; 2, medial collateral ligament bursitis; 3, meniscal cysts; 4, pes anserinus bursitis; 5, bursa between the iliotibial tract and lateral epicondyle.

Medial collateral ligament bursitis

The patient is usually middle-aged and complains of localized pain at the medial side of the knee, which has appeared without a specific cause (Fig. 52.18). The pain is worse during activity and eases at rest, but nocturnal pain may occur. There is no symptomatic evidence of internal derangement, such as twinges, locking and fear of giving way.¹⁵⁴ Spontaneous cure is uncommon¹⁵⁵: one of our patients had had unchanged symptoms for more than 6 years.