When in a healthy condition, both parts of the joint are surrounded by joint cartilage which acts as a lubricant in order to reduce friction. It additionally helps absorb shock; it distributes and reduces the forces which act upon the hip joint. The fixed joint capsule forms an envelope around the hip joint.
Stability and movement thanks to ligaments and muscles
It is the bony structure which makes this joint so very stable: The femoral head rests relatively securely in the amply sized concave acetabulum. The hip joint is also reinforced by strong ligaments. The joint is surrounded by strong muscles which help protect it and allow the legs to be moved with great force.