ARTHRITIS OF THE KNEE
The knee joint is the junction of three bones—the femur (thigh bone or upper leg bone), the tibia (shin bone or more prominent bone of the lower leg), and the patella (knee cap). The patella is about 2 to 3 inches wide and 3 to 4 inches long. It sits over the other bones at the front of the knee joint and slides when the leg moves. It protects the knee and gives leverage to muscles.
The ends of the three bones in the knee joints are covered with articular cartilage—a rigid, elastic material that helps absorb shock and allows the knee joint to move smoothly. Separating the knee bones are pads of connective tissue called menisci, divided into two crescent-shaped discs positioned between the tibia and femur on the outer and inner sides of each knee. The two menisci in each knee act as shock absorbers, cushioning the lower part of the leg from the weight of the rest of the body and enhancing stability.
WHAT IS ARTHRITIS OF THE KNEE?
Arthritis of the knee is most often osteoarthritis, a degenerative disease where the cartilage in the joint gradually wears away. In rheumatoid arthritis, which can also affect the knees, the joint becomes inflamed, and cartilage may be destroyed. Arthritis not only affects joints but may also affect supporting structures such as muscles, tendons, and ligaments. Osteoarthritis may be caused by excess joint stress, such as repeated injury, deformity, or if a person is overweight. It most often affects middle-aged and older people. A young person who develops osteoarthritis may have an inherited form of the disease or may have experienced continuous irritation from an unrepaired torn meniscus or another injury. Rheumatoid arthritis usually affects people at an earlier age than osteoarthritis.
SIGNS AND DIAGNOSIS
A person who has arthritis of the knee may experience pain, swelling and a decrease in knee motion. A common symptom is morning stiffness that lessens after moving around. Sometimes the knee joint locks or clicks when the knee is bent and straightened, but these signs may also occur in other knee disorders. The doctor may confirm the diagnosis by performing a physical examination and taking X-rays, which typically show a loss of joint space. Blood tests may help diagnose rheumatoid arthritis, but other tests may also be needed. Analysis of fluid from the knee joint may help diagnose some kinds of arthritis. The doctor may use arthroscopy to visualize the damage to cartilage, tendons, and ligaments directly and to confirm a diagnosis. Still, arthroscopy is usually done only if a repair procedure is to be performed.
TREATMENT
Most often, knee osteoarthritis is treated with analgesics (pain-reducing medicines), such as aspirin or acetaminophen; NSAIDs, such as ibuprofen, and exercises to restore joint movement and strengthen the knee. Losing excess weight can also help people with osteoarthritis. Rheumatoid arthritis of the knee may require a treatment plan that includes physical therapy and the more potent medications. In people with arthritis of the knee, a seriously damaged joint may need to be surgically replaced with an artificial one.