INTRODUCTION

Pain is the most common presenting symptom of knee abnormalities. The causes of knee pain tend to be age related. A convenient way to classify knee pain complaints is by age group and by whether the pain is intraarticular, periarticular, or referred (Table 11-3).

TABLE 11-3 INTRAARTICULAR KNEE PAIN DIFFERENTIATED BY AGE

Adapted from Klippel JH, Dieppe PA: Rheumatology, vol 1-2, ed 2, London, 1998, Mosby.

TABLE 11-2 KNEE CROSS-REFERENCE TABLE BY SUSPECTED SYNDROME OR TISSUE

The rounded contour of the femoral condyles furnishes little stability and the flat tibial plateaus, deepened by the semilunar cartilages. The quadriceps muscle and its tendinous expansions are great contributors to the stability and function of the knee. The earliest clinical indication of internal knee derangement is atrophy of the quadriceps.

The knee is not a true hinge joint. The tibia navigates a helical course on the condyles of the femur. Most traumatic arthritis of the knee in middle-age and elderly people results from minor derangements of the soft tissues, especially the menisci.

The knee lacks the stability of the hip, which has its ball and socket, or the ankle, which has its mortise and tendon. Both the hip and the ankle have structures that give some degree of bony stability. In the knee joint, the socket of the top of the tibia is so minimal that the lateral tibial plateau may be flat or even convex. The little bit of buffering provided by the menisci gives minimal increase in stability because the menisci are unstable themselves. For stability, the knee must depend largely on the soft tissues, ligaments, capsule, and muscles.

Making an accurate diagnosis about the exact nature of the patient’s knee injury is extremely important. Examination must determine what part of the knee is injured and how bad the injury is.

ESSENTIAL ANATOMY

The knee joint is the articulation of the femur, patella, and tibia. The fibula is not involved in this articulation. The knee allows for flexion and extension and for rotation when the knee is in complete flexion but not if the knee is fully extended.

ESSENTIAL MOTION ASSESSMENT

The flexion-extension movement of the knee is not a simple hinge motion (Figs. 11-1 and 11-2). As the knee passes through its degrees of flexion and extensions, the imaginary mediolateral axis through which the movement occurs shifts up and down on the femur.

FIG. 11-1 The normal angle of knee flexion ranges from 130 to 150 degrees.

FIG. 11-2 The knee should normally extend to a straight line (0 degrees) and can occasionally be hyperextended up to 15 degrees.

ESSENTIAL MUSCLE FUNCTION ASSESSMENT

The examiner tests the muscles responsible for knee flexion and extension, the hamstrings and quadriceps, respectively (Figs. 11-3 and 11-4).

FIG. 11-3 The prime movers involved in flexion of the knee are the biceps femoris (sciatic nerve, tibial branch, S1, S2, and S3 to the long head; peroneal branch, L4, L5, S1, and S2 to the short head), semitendinosus (sciatic nerve, tibial branch, L4, L5, S1, S2, and S3), and the semimembranosus (sciatic nerve, tibial branch, L4, L5, S1, S2, and S3) muscles. The patient flexes the knee through its range of motion.

FIG. 11-4 The prime mover involved in extension of the knee is the quadriceps femoris (rectus femoris, vastus intermedius, vastus medialis, and vastus lateralis) muscle (innervated by the femoral nerve, L2, L3, and L4). Extension of the knee is tested while the patient extends the knee through its range of motion.

ESSENTIAL IMAGING

The typical knee study consists of an anteroposterior (or posteroanterior) and a lateral view. Many examiners will include tangential, tunnel, or oblique views for further evaluation. The tangential view provides an axial depiction of the patella and its relationship with the femur. The tunnel allows excellent visualization of the intercondylar region of the femoral-tibial articulation.

ABDUCTION STRESS TEST

PROCEDURE

FIG. 11-5

ADDUCTION STRESS TEST

PROCEDURE

FIG. 11-6

APLEY COMPRESSION TEST

PROCEDURE

FIG. 11-7

FIG. 11-8

APPREHENSION TEST FOR THE PATELLA