There are a host of other muscles in both upper and lower limbs whose form and structure will repay careful study. Study of a macerated bone can at most teach one the precise bony attachment of a muscle. It tells nothing of other non-osseous attachments, nothing of the form of the living muscle that gives shape to the limb, and nothing of the surface structure of the muscles, knowledge of which can be used not only to recognise them at operation but to understand their normal function in relation to neighbouring parts.

1. The movements of flexion and extension at the knee joint take place above the menisci; the movements of rotation take place below the menisci.

2. The popliteus muscle consists of two halves, one being attached by tendon to the femur, the other by aponeurosis to the lateral meniscus. The action of the muscle is to rotate the knee and retract the posterior arch of the lateral meniscus. The flexing action of the muscle is quite negligible.

3. The effects of rotation of the knee joint on the two menisci are dissimilar. The medial meniscus is distorted during rotation; its horns move with the tibia, but the intervening arch moves with the femur, and the distortion renders it liable to injury during rotation. The lateral meniscus does not become distorted during rotation; it follows the lateral condyle of the femur by reason of the attachments of the ligaments of Humphry and Wrisberg and the popliteus muscle. It is thus relatively immune from injury daring rotation.