How does my knee work?
Your thigh bone (femur) turns on the upper end of the shin bone (tibia), while your kneecap (patella) slides in a groove on the end of the thigh bone. Bands of tissue called ligaments connect these two bones and help keep the knee joint steady. The long muscles on the front of the thigh, called quadriceps, help strengthen the knee.
A smooth substance (called articular cartilage) covers the surface of the bones where they touch each other within the joint, and acts as a cushion between the bones. A thin, smooth tissue liner (called the synovial membrane) covers the rest of the surfaces of the knee joint, and provides fluid that lubricates the joint and prevents your bones from rubbing against each other.