The knee joint is a complex structure designed to allow normal function whilst withstanding the huge stresses we put through it during everyday activities and sport. The main weight bearing part of the joint is formed between the two rounded ‘condyles’ on the end of the femur (the thigh bone) and the flatter top surface of the tibia (the shin bone).
The space between the condyles of the femur is called the ‘intercondylar notch’; this provides the surface attachments for two of the main ligaments in the knee. The notch extends forwards forming a groove at the front of the bone (the trochlea), the kneecap (patella) is situated at the front of the knee and is shaped to sit and glide in the trochlea during movement of the joint.
The knee is a ‘synovial hinge joint’ – this means that movement is restricted to one plane – ie. bending and straightening in a forward / backward direction. This however, is rather too simplistic – the knee is a complex structure where some rotation also occurs, thus allowing a locking and unlocking mechanism to take place.
All joints in the body that allow voluntary movement, are enclosed by a fibrous capsule; this is lined with a special ‘synovial’ membrane which produces fluid to keep the joint surfaces lubricated and healthy.