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ANATOMY

The knee consists of two joints, the tibiofemoral joint and the patellofemoral joint. Within the tibiofemoral joint, the distal femur (comprised of the medial and lateral femoral condyles) articulates with the proximal tibia (comprised of the medial and lateral tibial condyles) (Figure 274-1). The medial and lateral menisci are situated between the articular surfaces, and the menisci provide cushion, lubrication, and resistance to articular wear (Figure 274-2). In the patellofemoral joint, the patella articulates with the distal femur along the anterior depression called the patellofemoral groove during flexion and extension of the knee. The patella is stabilized by the patellar tendon and medial retinaculum.

FIGURE 274-1.

The supracondylar and condylar areas of the femur, and the medial and subcondylar areas of the tibia.

FIGURE 274-2.

Ligaments of the right knee joint. The articular capsule and the patella have been removed.

There are four ligaments in the knee: the anterior cruciate ligament, the posterior cruciate ligament, and the medial and lateral collateral ligaments (Figure 274-2). These ligaments provide strength and stability to the knee. The posterior aspect of the knee, the popliteal fossa, contains the popliteal artery and vein, the common peroneal nerve, and the tibial nerve (Figure 274-3).

FIGURE 274-3.

Posterior knee: popliteal fossa anatomy.

CLINICAL FEATURES

Determine the mechanism of knee injury and review all prior orthopedic injuries or surgical procedures. Compare contralateral noninjured or normal joint with the injured joint, especially during ligament stress testing.

The first examination is usually the easiest to perform and may be the most valid, as a patient’s anticipatory pain or an effusion limiting the examination may not have yet developed.

Assess gait (if possible) and the ability to perform a straight leg raise (evaluates the extensor complex). Evaluate the knee for ecchymoses, swelling (extra-articular fluid), effusion (intra-articular fluid), masses, patella location and size, muscle mass, erythema, and evidence of local trauma. With the patient supine, determine whether leg lengths are equal or unequal. Ask the patient to demonstrate the best possible active range of motion. Assess distal neurovascular function. Palpate the nontender areas first and work toward the tender area to minimize patient apprehension. Include palpation of the patella, patellar facets, proximal fibula, and femoral and tibial condyles for pain and crepitus. Make note of joint effusion, tenderness, increased temperature, strength, sensation, and location of pulses.

Examine the patella for size, shape, and location with the knee in flexion. Assess patellar mobility with the knee in extension for lateral and medial movement without apprehension. Palpate the popliteal space for masses, swelling, and ...

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