Patient Education
Anatomy

Cartilage, a tough, lubricating tissue, covers the ends of bones in every joint. Cartilage functions to allow smooth, pain-free motion. Cartilage also cushions the bones during movement.

Knee
The knee is a hinge joint formed by the tibia (shinbone), femur (thighbone), and patella (kneecap). The bones in the joint are held together with ligaments, which are strong bands of tissue.

Hip
The hip is a ball-and-socket joint that allows the leg to move in a variety of positions. The bones in the hip are the femur (thighbone) and pelvis (hipbone). The femur is capped by the femoral head (ball), which fits into the acetabulum (socket). The bones in the joint are held together with ligaments, which are strong bands of tissue.

Shoulder
The shoulder joint contains the head of the humerus (upper arm bone) and the scapula (shoulder blade). The head of the humerus rides against the scapula in a tiny impression called the glenoid; think of this contact as a golf ball on a tee. The smaller size of the glenoid is what allows near unlimited range of motion in a healthy shoulder.