The knee joint consists of the distal end of the femur, the proximal end of the tibia and the patella, enclosed by a series of soft tissues surrounding the joint (ligaments, joint capsule and inter-articular menisci).It is one of the most complex joints in the human body.

The cartilage that covers the articular surfaces protects the bones from direct friction and facilitates the relative sliding during the movements of everyday life.

During flexion-extension movements of the leg, the action of the thigh muscles causes the femur to slide over the tibia and the patella to slide along the distal end of the femur.
The onset of some degenerative pathologies (arthrosis, arthritis) can lead to damage to the cartilage and to the reduction of its thickness: the bone surfaces therefore enter in direct contact causing pain.