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.
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.]
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
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 stress testing....