The knee is a vulnerable joint that bears a great deal of stress from everyday activities such as lifting and kneeling, and from high-impact activities such as jogging and aerobics.
The knee is formed by the following parts:
- tibia - shin bone or larger bone of the lower leg
- femur - thighbone or upper leg bone
- patella - kneecap
Each bone end is covered with a layer of cartilage that absorbs shock and protects the knee. Basically, the knee is two long leg bones held together by muscles, ligaments, menisci and tendons.
There are two 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 tissue that connect muscles to bones. Menisci act as shock absorbers. These are the two crescent-shaped discs of connective tissue located between the bones of the knee Ligaments are elastic bands of tissue that connect bone to bone. Some ligaments on the knee provide stability and protection of the joints, while other ligaments limit forward and backward movement of the tibia (shin bone). There are four main ligaments:
- anterior cruciate ligament (ACL) – the ligament located in the center of the knee that controls rotation and forward movement of the tibia (shin bone)
- posterior cruciate ligament (PCL) – the ligament located in the center of the knee, that controls backward movement of the tibia (shin bone)
- medial collateral ligament (MCL) – the ligament that gives stability to the inner knee
- lateral collateral ligament (LCL) – the ligament that gives stability to the outer knee