The knee joint is the largest joint in the body. It is predominantly called a hinge joint, but also glides and rotates. It is comprised of the lower end of the thigh bone, the femur and the upper end of the leg bone or tibia as well as the knee cap or patella. The knee joint is thought to consist of three parts: the medial compartment or inner aspect of the knee, the lateral compartment or the outer aspect of the knee, and the patellofemoral compartment, where the knee cap articulates with the front of the lower femur.
The knee joint has three parts. The thigh bone (the femur) meets the large shin bone (the tibia) to form the main knee joint. This joint has an inner (medial) and an outer (lateral) compartment. The kneecap (the patella) joins the femur to form a third joint, called the patellofemoral joint. The patella protects the front of the knee joint. See the entire definition of Knee joint