Article updated and reviewed by Stephen Burnett, MD, FRCS(C), Assistant Professor, Department of Orthopaedic Surgery, Washington University School of Medicine on July 11, 2005.
A degeneration or ‘wear and tear’ of articular (joint surface) cartilage usually accompanied by an overgrowth of bone (osteophytes), narrowing of the joint space, sclerosis or hardening of bone at the joint surface, and deformity in joints. OA is not usually associated with inflammation, although swelling of the joint does frequently occur in OA. This type of arthritis is called osteoarthritis, OA, degenerative joint disease, DJD, or osteoarthrosis. Other forms of arthritis (rheumatoid, post-traumatic, and other inflammatory disorders) frequently may have OA as the end-stage, making differentiation difficult.
The tissues involved most in osteoarthritis are the cartilage and underlying subchondral bone. The cartilage is the smooth white material that forms over the ends of the bones and forms the moving surface of the joint on both sides. Cartilage is tough, elastic, very durable, and comprised of collagen and water molecules. Cartilage does not have a blood supply and receives its oxygen and nutrition from the surrounding joint fluid by diffusion. The ability of cartilage to absorb nutrients and fluid allows it to function without a blood supply.
When we move a joint, the pressure across the joint expresses fluid and waste products out of the cartilage cells, and when the pressure is relieved, the fluid diffuses back, together with oxygen and nutrients. Hence the health of the cartilage depends on movement of the joint.
Over many years and with activity and use of a joint, the cartilage may become frayed, injured, torn, and may even wear away entirely. When this occurs, the bone surface on one side of the joint tends to rub or glide against the bone on the opposite side of the joint, providing a less elastic joint surface, and generating higher contact pressures at the end of the bone. Over time, the contacting bone surfaces become hardened and ‘sclerotic’, a process that causes the bone to look polished and on x-rays produces a whitened appearance.
There are three common forms of osteoarthritis, and many people have some of each type. All people will develop OA to some degree, involving one or more joints, throughout their lifetime as the aging process advances. The most common sites for OA include the base of the thumb joint, the knees, and the hands.
The first and mildest form causes bony enlargement of the finger joints. The end joints of the fingers become bony (this is due to osteophyte formation, or reactive bone at the joint surfaces) and the hand begins to assume the appearance we associate with old age – i.e., a swollen joint involving the fingers. The base of the thumb may become swollen with bony enlargement and is the most frequently encountered site of OA.
The second form involves the spine (neck and mid- and low-back regions). Bony growths (osteophytes) appear on the spine in the neck region or in the lower back. Usually the bony growths are associated with some narrowing of the space between the vertebrae. Similar to the long-bone cartilage joint space degeneration, the process of OA in the spine begins with a degeneration of the cartilage in the disc spaces. These disc spaces degenerate, narrow, and lead to increased forces on the bones, with subsequent osteophyte formation.
The third form involves the weight-bearing joints,most frequently involving the knees, which are followed by the hips.
The symptoms of OA may become quite severe. Osteoarthritis of the weight-bearing joints, particularly the hip and knee, develops slowly and often (but not always) involves both sides of the body. Pain in the joint may remain fairly constant or may wax and wane for a period of years, and usually is activity related. In advanced cases, walking or regular activities of daily living may become difficult or even impossible. Reactive fluid (an effusion) may accumulate in the affected joint, giving it a swollen appearance. This fluid is generated from the soft tissue in the knee known as synovium, which reacts by trying to create more lubrication to make the joint surfaces smoother. A knee may feel unsteady, stiff, or have a sensation of giving out when weight is placed on it. Additionally, a feeling of locking or grinding may be felt in the joint.
Usually, in the knee, the osteoarthritis will affect the inner half of the joint more than the outer. This may result in progressive deformity with the leg becoming bowed and may cause difficulty in walking. OA involving the outer half of the knee may cause a “knock-knee” appearance. Generally, this form and deformity of arthritis is less common, and it is more often associated with other forms of arthritis, such as rheumatoid arthritis.
Osteoarthritis is the most common form of joint disease, sparing no age, race, or geographic area. At least 20 million adults in the U.S. suffer from osteoarthritis. Symptomatic disease increases with age. Many patients may have OA seen on x-rays, but not be overly symptomatic.
Hereditary, injury, fractures around a joint surface, and overuse factors are most frequently involved in the development of osteoarthritis. Osteoarthritis may occur secondary to an injury to the joint due to a fracture, repetitive or overuse injury, or metabolic disorders (e.g., hyperparathyroidism). Additionally, gout and other forms of crystalline joint disease may lead to OA of a joint. Obesity or being overweight is a risk factor for knee osteoarthritis more commonly in females; this is less commonly seen in the hip joint. Recreational running does not increase the incidence of OA, but participation in competitive contact sports does. Specifically, impact sports that repetitively load a joint increase the injury to a joint. If cartilage in a joint is injured, it cannot regenerate, and the new forces that are created are abnormal, leading to further stresses, and the cycle may propagate.
Initially there may be joint stiffness, usually lasting more than 15 minutes, and typically following activity of the joint. Later there may be pain on motion of the affected joint, which is made worse with activity or weight-bearing and relieved by rest. Typically OA improves with rest and does not remain symptomatic at night time. It is usually better in the morning, and it worsens as the day progresses.
There may be limitation of motion of the affected joint, although this is a later finding. Coarse crepitus (a creaking or cracking) may be felt in the joint. There is usually some mild joint swelling and tenderness to touch. The joint may feel warm. A joint that cracks and snaps does not necessarily mean arthritis is present, and many patients are able to make their joints crack without having pain.
Diagnosis is based on the medical history, physical examination, and x-ray findings. Lab tests do not reveal signs of inflammation, but may be performed to rule out other arthritic disorders.
Treatment of OA depends upon multiple factors including patient age, activities, medical condition, and x-ray findings. Patients with mild to moderate osteoarthritis of weight-bearing joints (hips and knees) may benefit from a supervised exercise program such as walking. Non-impact activities such as swimming, cycling, and walking tend to be more comfortable for patients with OA. In a younger patient with signs or symptoms of OA, other causes of arthritis such as deformity, medical conditions, or bone disorders should be carefully sought for in order to rule out other conditions.
A program of regular physical activity can strengthen the muscles, tendons, and ligaments surrounding the affected joints and preserve mobility in joints that are developing bone spurs. Many physicians believe that osteoarthritis may be prevented by good health habits. Remaining active, maintaining an ideal body weight, and exercising the muscles and joints regularly so as to nourish cartilage.
A first line of simple treatment - acetaminophen (Tylenol) is as effective and has less side effects than other non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen, naproxen, or aspirin.
Glucosamine-chondroitin sulfate may be prescribed by your doctor. This medication, when taken over a period of months, may reduce pain and symptoms by restoring or replenishing nutrition to diseased cartilage cells. It tends to be more effective in earlier stages of OA. The dosage and combination of each ingredient is an important aspect of the therapy, as not all preparations and brands are the same. Patients who fail to improve on acetaminophen or glucosamine may be treated with salicylates and other oral anti-inflammatories ( NSAIDs). Previously, medications such as Vioxx, Celebrex, and Bextra (Cox-2 NSAIDS) were preferred due to less gastrointestinal side effects (ulcers) and improved pain relief for arthritis. However, currently the use of these medications should be reviewed with your doctor, as concerns about their use in certain patients has been recently reported. More traditional NSAIDS (ibuprofen, naproxen, etc.) are available over the counter, and they also provide excellent relief of symptoms. Capsaicin cream 0.25% applied twice daily may reduce knee pain. Intra-articular (within the joint) injections of steroids may also be helpful, although the duration and amount of pain relief is often unpredictable, especially in more advanced stages of OA. Alternative injections of hyaluronic acid peparations (sodium hyaluronate) are also available and may be very useful in the treatment of OA. These injections are indicated for OA of the knee, and typically require an injection once a week, over a period of three to five weeks (i.e., three to five injections). The hyaluronic acid is injected into the knee joint, and similar to oral glucosamine, may provide nutrition to the diseased cartilage cells and collagen within the cartilage. The fluid is a gel-like material that appears to act initially like a lubricant for the joint. However, studies have shown that the lubricant aspect plays little role and, in fact, the fluid is absorbed quickly by the cartilage cells.
Bracing, splinting, and other orthotic treatments may be useful in managing or “unloading” an arthritic joint surface. These nonoperative treatments are simple, often effective, however cost and ease of use are factors in their selection in treatment.
Surgery may be dramatically effective for patients with severe osteoarthritis of the weight-bearing joints. Total hip replacement and newer hip resurfacing replacements and total knee replacement or unicompartmental (partial) knee replacement can be extremely effective. Joint replacement is now being performed in younger patients also. The concerns about wear of the prosthetic joint surface in younger patients make this the most challenging aspect of future research in this area. Newer joint surfaces for joint replacement including highly cross-linked polyethylene, metal on metal bearing, ceramic bearings, and others have emerged and currently are available in the U.S.
Although arthroscopic surgery for knee osteoarthritis is a common procedure, its long-term effectiveness is unclear, and may be best for symptoms such as catching, locking, or those that have been present for only a short duration. In addition, not all patients that have arthritis should have an arthroscopy, as this may not improve their symptoms.
In younger patients, hip and knee preserving procedures should be considered, in order to avoid a hip or knee replacement. Although performed less frequently, hip and knee preserving procedures, such as osteotomy (cutting the bone and realigning the bone or joint surface), may restore a joint to a normal alignment and be an excellent alternative to joint replacement.
Editorial review provided by VeriMed Healthcare Network.
Experimental techniques to repair cartilage loss in the knee by transplantation of cartilage cells is promising. This is most effective in small, localized areas of cartilage loss and not in advanced arthritis. These procedures also may be combined with joint osteotomy to alter joint alignment in order to allow this new cartilage to heal.
Weight reduction may reduce the risk of symptomatic knee osteoarthritis and, more importantly, reduce the symptoms of OA in the knee in overweigh patients.
If you have an injury to your joint, activity modification while maintaining an active lifestyle and joint range of motion provide for a healthy joint recovery.