AnAtomy of Common ProCedures
The applied anatomy of examination of the knee
Injuries of the knee are common. Accurate diagnosis of the precise site of structural damage entirely depends on a clear knowlege of its anatomy. The knee is a hinge joint, made up of the articulations between the femoral and tibial condyles and between the patella and the patellar surface of the femur(Figure 1). The capsule of the joint is attached to the margins of these articular surfaces, but it communicates superiorly with the suprapatellar bursa, which extends a handsbreadth above the patella between the lower femoral shaft and the quadriceps muscle. An effusion of blood or serous exudate following trauma produces a characteristic swelling above the patella; often the diagnosis can be madeat a glance. The joint capsule also communicates posteriorly with a bursa under the the medial head of gastrocnemius and often, through it, with a bursa under the tendon of semitendinosus – a common site for cyst formation. Anteriorly, the capsule is powerfully strengthened by the ligamentum patellae and, on either side, by the medial and lateral collateral ligaments. The latter passes to thehead of the fibula, which is easily felt, and therefore lies free from the capsule (Figure 1). Within the knee joint are a number of important structures (Figures 1 and 2). The cruciate ligaments are extremely strong bands between the tibia and femur. They arise from the anterior and posterior intercondylar areas of the superior aspect of the tibia, taking their names from their tibial origins, andpass obliquely upwards to attach onto the intercondylar notch of the femur. The function of the anterior cruciate is to resist forward movement of the tibia on the femur and it becomes taut in forward displacement of the knee. It also resists rotational strain. The posterior cruciate resists backward displacement of the tibia (Figure 3).
Professor Harold Ellis is Clinical Anatomist, Guy’s, King’sand St Thomas’ School of Biomedical Science, London SE1 1UL
The semilunar cartilages (menisci) are crescent-shaped and are triangular in cross
section, the medial being larger and less curved than the lateral (Figure 2). They
Figure 1. The knee, anterior view. The knee is flexed and the patella has been turned downwards.
Lateral collateral ligament Posterior cruciate ligament Lateralsemilunar cartilage Anterior cruciate ligament Popliteus tendon Medial semilunar cartilage
Medial collateral ligament
Figure 2. The right knee in transverse section, looking down onto the tibial condyles.
Patellar ligament (turned down) Tuberosity of tibia
Transverse ligament of knee
Anterior cruciate ligament
Medial meniscusLateral meniscus
Posterior cruciate ligament
British Journal of Hospital Medicine, May 2010, Vol 71, No 5
AnAtomy of Common ProCedures
are attached by their tips to the tibial intercondylar area and by their periphery to the joint capsule, although the lateral cartilage is only loosely adherent, and therefore less likely to be trapped and torn in rotational injuries of the knee thanthe medial cartilage. These cartilages deepen, but only to a negligible extent, the articulations between the femoral and tibial condyles. Their function is probably to act as shock absorbers. However, if both cartilages are removed, the knee can regain complete functional efficiency. An infrapatellar pad of fat fills the space between the patellar ligament and the femoral intercondyiar notch. Thesynovium which covers this pad projects into the joint as the alar fold on each side. The main movements of the knee are flexion and extension, but note on yourself when standing that, when the knee is flexed, some degree of rotation is possible. In full extension the medial condyle of the tibia, being larger than the lateral, rides forwards on the medial femoral condyle, thus ‘screwing’ the...
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