Chapter 271

The emergency physician must be familiar with the examination of the normal and abnormal knee to be able to recognize, treat, and make appropriate referrals for specific injuries. The first examination is usually the easiest to perform and may be the most valid, because the patient does not anticipate pain and therefore does not guard against the examination and because inflammation and effusion further limiting the examination may not yet have occurred.

Within the knee 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 271-1). The medial and lateral menisci are situated between the articular surfaces, and the menisci provide cushion, lubrication, and resistance to articular wear (Figure 271-2). The patella articulates with the distal femur along the patellofemoral groove. The patellofemoral groove is the depression in the anterior aspect of the distal femur that allows the patella to slide along the femur with flexion and extension of the knee.

###### Figure 271-1.

The supracondylar and condylar areas of the femur, and the medial and subcondylar areas of the tibia. [Modified with permission from Hohl M, Larson RL: Fractures and dislocations of the knee, in Rockwood CA Jr, Green DP (eds): Fractures, Vol. 2. Philadelphia, JB Lippincott, 1975, pp. 1132, 1147.]

###### Figure 271-2.

Ligaments of the right knee joint. The articular capsule and the patella have been removed. (Reproduced with permission from Spencer AP, Mason EB: Human Anatomy and Physiology. Menlo Park, CA: Benjamin/Cummings, 1979, p. 174.)

There are four ligaments in the knee: the anterior and posterior cruciate ligaments and the medial and lateral collateral ligaments (Figure 271-2). 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 perineal nerve, and the tibial nerve.

The knee examination consists of five components: history, observation, inspection, palpation, and stress testing (see video: The Knee Exam).

Determine the mechanism of knee injury and review all prior orthopedic injuries or surgical procedures. Assess gait (if possible), functional range of motion, and the ability of the patient to extend the flexed knee against minimal resistance. Inspect the knee for swelling, ecchymoses, effusion, 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. Last, ask the patient to demonstrate the best possible active range of motion. Assess pulses and distal neurologic function. As with all orthopedic examinations, the noninjured or normal knee should be compared with the injured knee during all aspects of the examination, but especially during palpation and ...

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