Osteoarthritis, the "wear and tear" degenerative joint disorder, affects approximately 15.8 million Americans, most of whom are over 45.  Since it is a very common cause of knee and hip pain, the condition is often taken for granted during the senior years. However, it's also important to realize that not all knee and hip pain may be due to arthritis. 

Here are a number of other musculoskeletal disorders that can cause significant pain in the knees or hips:

Bursitis -- Painful inflammation of a bursa, a flat sac containing fluid that aids in the movement of joints and muscles and reduces friction. Acute bursitis occurs suddenly; the inflamed area is painful when moved or touched, and the skin joint can be red and swollen. The condition can also become chronic, with recurrent attacks. Persistent redness and swelling can also be a sign of joint infection and should probably be evaluated by a physician.

Tendonitis -- Inflammation of a tendon, the fibrous cords of tough tissue that connect muscles to bones. Moving joints near an inflamed tendon may cause severe pain.

Synovitis -- Inflammation of the synovial membrane, the layer of smooth, slippery tissue that lines the joints and surrounds tendons. The affected joint becomes swollen and painful, especially when moved.

Torn cartilage -- Injury to the cartilage (the tough, elastic material covering the bones in the joints) or to the menisci (pads of connective tissue separating the bones) can be caused by forceful impact or by sudden, awkward movements.

Fractures -- Older people may suffer bone fractures (breaks) as a result of osteoporosis, the bone-thinning disease that depletes bones of strength. When bones are brittle, even mild stresses can cause small fractures.

These are just a few of the most common causes of joint-related pain. Many of these conditions have similar symptoms, including pain, swelling, stiffness and heat. Though symptoms are common, treatment for these conditions vary depending on the diagnosis. Consulting with your physician or an orthopedist is the best means of diagnosing and properly treating knee or hip pain.