A healthy knee bends easily. The joint absorbs stress and glides smoothly. This allows you to walk, squat and turn without pain. But when the knee is damaged, the joint may lose it’s ability to cushion stress. You may feel pain during movement. Sometimes a damaged knee joint will swell and hurt even when you are at rest.
A healthy knee
The knee is a hinge joint, formed where the thigh bone and shin bone meet. When the knee is healthy, the joint moves freely. This is because the joint is covered with slippery tissue and powered by large muscles.
- Cartilage is a layer of smooth, soft tissue. It covers the ends of the thigh bone and shin bone and it lines the underside of the kneecap. Healthy cartilage absorbs stress and allows the knee to glide easily.
- Ligaments are another type of soft tissue. They hold the bones of the joint together.
- Muscles power the knee and leg for movement.
- Tendons attach the muscles to the bones.
Years of normal use can cause cartilage to crack and wear away (Osteoarthritis). As exposed bones rub together, they become rough and pitted. The joint grinds. Being overweight or having an alignment problem, such as knocked or bowed knees, puts extra force on the joint. this may speed up the damage.
A chronic disease such as rheumatoid arthritis or gout can cause swelling and heat (inflammation) in the joint lining. As the disease progresses, cartilage may be worn away and the joint may stiffen.
A bad fall or blow to the knee can injure the joint. If the injury does not heal properly, extra force may be placed on the joint. Over time this can cause the cartilage to wear away (traumatic arthritis).