Clinical examination of the knee

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Clinical examination of the knee

Chapter contents

Referred pain

Pain referred to the knee

The front of the knee represents the second and third lumbar dermatomes. Two structures, the hip and third lumbar nerve root, are apt to give rise to referred pain in this area. When referred pain to the knee is suspected, the diagnostic points in the history are the indefinite area of complaint and radiation ‘upwards’ along the anterior aspect of the thigh. When asked for the exact site of pain, the patient points to the whole suprapatellar area and the front of the thigh. In vague anterior knee pain, the lumbar spine and the hip joint must be examined immediately. This is especially so in children who complain of knee pain but who are in fact developing hip disease, such as aseptic necrosis or epiphysiolysis. Another common error is to take a radiograph of an elderly person’s knee because the pain is felt here, and then almost certainly to find some osteoarthrosis at the knee but to miss the osteoarthrotic hip.

The back of the knee is innervated by the first and second sacral segments. Disorders of the first and second sacral roots, and also the sacroiliac joints, can refer pain to this area. Again, the patient cannot point exactly to the site of pain. The pain distribution remains vague and spreads upwards along the thigh or downwards in the calf. There is also no history of relevant trauma. Compression of S1, caused either by a primary posterolateral protrusion in a young adult or by a narrowed lateral recess in an elderly person, may also provoke pain at the back of the knee only. As pain is not felt in the back or buttock at the onset, the symptoms do not draw immediate attention to the possibility of a lumbar disorder. Once again, a careful history suggests the diagnosis. With a primary posterolateral protrusion, the patient will have noticed that sitting and coughing hurt the knee, whereas walking does not. In compression of the nerve root in a narrow lateral canal, complaints are related to walking and standing, whereas bending usually relieves the pain.

Pain referred from the knee

Lesions of the knee are usually located accurately by the patient at or in the knee. Sometimes an impacted loose body complicating osteoarthrosis can cause pain referred down the leg and slightly up the thigh but this is rather exceptional.

History

Knee problems are always difficult to evaluate and every possible assistance is needed to make a proper diagnosis. A chronological history, as summarized in Box 50.1, is therefore the first, and sometimes even the most important, element. Cyriax used to say that one who ‘doesn’t have a diagnosis after the history, will hardly get one after the clinical examination’.

Age is a very important factor because some disorders at the knee appear at a certain time of life only. Anterior knee pain in an adolescent can be the outcome of Osgood–Schlatter disease, whereas the same pain in a 30-year-old sportsman is the result of infrapatellar tendinitis and in a 50-year-old lady patellofemoral arthrosis. Symptoms of internal derangement in a 17-year-old boy almost certainly indicate osteochondritis dissecans, while in a 25-year-old sportsman they may suggest a meniscus lesion and in a 60-year-old lady are probably the result of impaction of a small loose body.

The patient should be questioned about occupation and sporting activities.

In knee problems there are three important symptoms that provide a great deal of information: ‘locking’, ‘twinge’ and a ‘feeling of giving way’. Because the meaning of these words is not always totally understood and patients frequently confuse them, it is vital to describe what exactly is meant when asking about these symptoms.

• Locking: sudden (painful) limitation occurs during a movement, whereas other movements are free and painless. The knee can be locked in flexion (extension being limited) or extension (flexion being impossible).

• Twinge: a sudden, sharp and unexpected pain is felt. For example, the patient feels abrupt, unforeseen and sharp pain at the inner side of the knee during walking. The pain disappears immediately and normal walking again becomes possible.

• Feeling of giving way: this is the typical sensation in instability – a sudden feeling of weakness. It feels as if the knee cannot bear the body weight during a particular movement. The knee tends to ‘collapse’.

In order to work out the diagnosis systematically and chronologically, it is as well to start with the onset of the symptoms before concentrating on symptoms at the time of examination.

Onset

• When did it start? Is this an acute, subacute or chronic problem?

• How did it start? Did the pain come on for no apparent reason or was there an injury?

If there was trauma

Describe the exact mechanism:

• In what position were the body and the leg?

• What forces were acting on the knee?

Describe the immediate symptoms:

• Where was the initial pain? At one side, all over or inside the joint?

• Was there any swelling? Immediately or after some time? An immediate effusion is always haemorrhagic and therefore indicates a serious lesion. If a swelling appears after some time, it is the consequence of a synovial reaction.

• Did the knee give way? Immediately or after some time?

• Was there any locking? If so, was the knee locked in flexion (which is typical for meniscal lesions) or was it in extension (as in impacted loose bodies from osteochondritis dissecans)? How did the knee become unlocked? By manipulation (meniscus) or spontaneously (loose body)?

• Were you still able to walk home after the accident?

If there was no trauma

• Did the pain come on suddenly or gradually?

• What were you doing when the pain first appeared?

• Describe the first symptoms. These may include localization, swelling, locking or loss of function (see above).

Evolution

In long-standing cases or in traumatic conditions, it is very important to have an exact idea of the evolution of the complaints.

• Did the pain change from one side of the joint to the other or did the pain spread? Pain moving from one side of the joint to another is characteristic of a loose body: the localization of the pain travels with the impacted loose fragment.

• What was the evolution of the swelling?

• For how long were you disabled?

• What treatment did you have and to what effect?

• Have there been any recurrences? If so, what brought them on and how did they progress?

Current symptoms

Finally, the current complaint is discussed.

• Describe the exact localization.

• What brings the pain on?

• Do you have nocturnal pain or morning stiffness? Pain at night usually indicates a high degree of inflammation. It occurs in acute ligamentous lesions, haemarthrosis and arthritis. Long-standing morning stiffness is usually an indication of rheumatic inflammation.

• What is the effect of going upstairs and downstairs, and which is the more troublesome? Going downstairs loads not only the extensor mechanism but also the posterior cruciate ligament and the popliteus tendon. Going downstairs is also very painful in impacted loose bodies.

• Do you have twinges?

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