Most of the time, the cause of OA is unknown. It is mainly related to aging, but metabolic, genetic, chemical, and mechanical factors can also lead to OA.
The symptoms of osteoarthritis usually appear in middle age and almost everyone has them by age 70. Before age 55, the condition occurs equally in both sexes. However, after 55, it is more common in women.
The disease causes the cushioning (cartilage) between the bone joints to wear away. As the disease gets worse, the cartilage disappears and the bone rubs on bone. Bony spurs usually form around the joint.
OA can be primary or secondary.
Primary OA occurs without any type of injury or obvious cause.
Secondary OA is osteoarthritis due to another disease or condition. The most common causes of secondary OA are:
Aging changes in the bones - muscles - joints (5 images)(Doctor-Reviewed information)
Changes in posture and gait (walking pattern) are as universally associated with aging as changes in the skin and hair. The skeleton provides support and structure to the body. Joints are the areas where bones come together. They allow the skeleton to be flexible for movement. In a joint, bones do not directly contact each other. Instead, they are cushioned by cartilage in the joint, synovial membranes around the joint, and fluid. Muscles provide the force and strength to move the body. Coordination is directed by the brain but is affected by changes in the muscles and joints. Changes in the posture and gait, weakness, and slowed movement are caused by changes in the muscles, joints, and bones. AGING CHANGES Bone mass or density is lost as people age, especially in women after menopause. The bones lose calcium and other minerals. The spine is made up of bones called vertebrae. Between each bone is a gel-like cushion (intervertebral disk. The trunk becomes shorter as the disks gradually lose fluid and become thinner. In addition, vertebrae lose some of their mineral content, making each bone thinner. The spinal column becomes curved and compressed (packed together. Bone spurs, caused by aging and overall use of the spine, may also form on the vertebrae. The shoulder blades (scapulae) and other bones may become porous. On an x-ray they may look "moth-eaten." The foot arches become less pronounced, contributing to slight loss of height. The long bones of the arms and legs, although more brittle because of mineral losses, do not change length. This makes the arms and legs look longer when compared with the shortened trunk. The joints become stiffer and less flexible. Fluid in the joints may decrease, and the cartilage may begin to rub together and erode. Minerals may deposit in some joints (calcification. This is common in the shoulder. Hip and knee joints may begin to lose structure (degenerative changes. The finger joints lose cartilage and the bones thicken slightly. Finger joint changes are more common in women and may be hereditary. Some joints, such as the ankle, typically change very little with aging. Lean body mass decreases, caused in part by loss of muscle tissue (atrophy. The rate and extent of muscle changes seems to be genetically determined. Muscle changes often begin in the 20s in men and the 40s in women. Lipofuscin (an age-related pigment) and fat are deposited in muscle tissue. The muscle fibers shrink. Muscle tissue is replaced more slowly, and lost muscle tissue may be replaced with a tough fibrous tissue. This is most noticeable in the hands, which may appear thin and bony. Changes in the muscle tissue, combined with normal aging changes in the nervous system, cause muscles to have reduced tone and ability to contract. Muscles may become rigid with age and may lose tone even with regular exercise. EFFECT OF CHANGES Bones become more brittle and may break more easily. Overall height decreases, mainly because of shortening of the trunk and spine. Inflammation, pain, stiffness, and deformity may result from breakdown of the joint structures. Almost all elderly people are affected by joint changes, ranging from minor stiffness to severe arthritis. The posture may become progressively stooped (bent) and the knees and hips more flexed. The neck may become tilted, and the shoulders may narrow while the pelvis may become wider. Movement slows and may become limited. The walking pattern (gait) becomes slower and shorter. Walking may become unsteady, and there is less arm swinging. Fatigue occurs more readily, and overall energy may be reduced. Strength and endurance change. Loss of muscle mass reduces strength. However, endurance may be enhanced somewhat by changes in the muscle fibers. Aging athletes with healthy hearts Reviewer: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 08/10/2008
Joint pain (2 images)(Doctor-Reviewed information)
Joint pain can affect one or more joints. See also: Arthritis (inflammation of joints; Bursitis; Muscle pain. Reviewer: Neil J. Gonter, M.D., Assistant Professor of Medicine, Columbia University, NY and private practice specializing in Rheumatology at Rheumatology Associates of North Jersey, Teaneck, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 04/24/2008
Joint x-ray(Doctor-Reviewed information)
This test is an x-ray of a knee, shoulder, hip, wrist, ankle, or other joint. Reviewer: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 05/02/2009
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