Joints are the areas where 2 or more bones meet. Most joints are mobile, allowing the bones to move. Basically, the knee is 2 long leg bones held together by muscles, ligaments, and tendons. Each bone end is covered with a layer of cartilage that absorbs shock and protects the knee.

There are 2 groups of muscles involved in the knee, including the quadriceps muscles (located on the front of the thighs), which straighten the legs, and the hamstring muscles (located on the back of the thighs), which bend the leg at the knee.

Tendons are tough cords of connective tissue that connect muscles to bones. Ligaments are elastic bands of tissue that connect bone to bone. Some ligaments of the knee provide stability and protection of the joints, while other ligaments limit forward and backward movement of the tibia (shin bone).

The knee consists of the following:

• Tibia. This is the shin bone or larger bone of the lower leg.
• Femur. This is the thighbone or upper leg bone.
• Patella. This is the kneecap.
• Cartilage. A type of tissue that covers the surface of a bone at a joint. Cartilage helps reduce the friction of movement within a joint.
• Synovial membrane. A tissue that lines the joint and seals it into a joint capsule. The synovial membrane secretes synovial fluid (a clear, sticky fluid) around the joint to lubricate it.
• Ligament. A type of tough, elastic connective tissue that surrounds the joint to give support and limits the joint’s movement.
• Tendon. A type of tough connective tissue that connects muscles to bones and helps to control movement of the joint.
• Meniscus. A curved part of cartilage in the knees and other joints that acts as a shock absorber, increases contact area, and deepens the knee joint.