Osteoarthritis

A disorder of hyaline cartilage and subchondral bone, primarily affecting the hand joints, spine, and joints of the lower extremity.

Osteoarthritis is the most common joint disease and is a leading cause of disability in persons > 65 years. It is probably not one disease but several having similar clinical and pathologic features. Thus, the typical changes (eg, cartilage deterioration, bony remodeling) can occur in several diarthrodial joints, but the causes may differ.

Primary (idiopathic) osteoarthritis affects the distal and proximal interphalangeal joints, first carpometacarpal joints, cervical and lumbar spine, hips, knees, and toes. The metacarpophalangeal joints, wrists, elbows, shoulders, and ankles usually are spared. Secondary osteoarthritis affects any joint that has been damaged by trauma or inflammation.

Aging alone does not cause osteoarthritis, although age-related cellular or matrix alterations in cartilage probably predispose elderly persons to the disease. Other possible predisposing factors include obesity, trauma, congenital abnormalities (eg, hip dysplasia), and primary joint disorders (eg, inflammatory arthritis).

Symptoms, Signs, and Diagnosis

Osteoarthritis is characterized by intermittent or constant joint pain that may be accompanied by limited movement, bone hypertrophy, and joint deformity. Pain is relieved by rest and exacerbated by movement and weight bearing; it is not associated with inflammatory symptoms such as redness and swelling. The disease usually progresses slowly.

In the hands, bony overgrowth of the distal interphalangeal joints (Heberden's nodes) and bony overgrowth of the proximal interphalangeal joints (Bouchard's nodes or nodules) may be present.

The diagnosis is based on a combination of clinical and x-ray findings. Characteristic x-ray findings include osteophytes, subchondral sclerosis and cysts, and asymmetric loss of joint space (implying degeneration of cartilage). However, conventional x-rays are not sensitive for detecting early osteoarthritis because they do not show pathologic changes in cartilage. Moreover, x-ray findings may be present without symptoms. MRI is more sensitive than conventional x-rays but should not be used routinely to diagnose osteoarthritis. The ESR and white blood cell (WBC) count are normal, and no autoantibodies are present. Synovial fluid analysis shows only mild leukocytosis (a WBC count of < 2000/µL).

Treatment

Comprehensive management involves a balance of cognitive-behavioral, physical, pharmaceutical, and surgical measures. The goals of treatment are to relieve pain and to minimize functional limitations. The patient's functional deficits and preferences for treatment must be considered. The patient should be taught about the chronic nature of the disease; unrealistic treatment expectations can lead to frustration and depression and can impair the patient-physician relationship. Asymptomatic osteoarthritis, diagnosed by x-ray findings, does not require treatment.

Nonpharmacologic measures: Nonpharmacologic measures are the cornerstone of therapy and should be used in all patients. Cognitive-behavioral therapy that is directed toward coping skills and self-efficacy (confidence in performing activities safely) is highly effective in improving function.

A regimen of range-of-motion, strengthening, and endurance exercises is important for pain relief and restoration of function. Adaptive aids (eg, braces, canes, devices to increase hand function) may be indicated to restore function and improve independence. Weight loss is important for obese patients.

Pharmacotherapy: Drugs should be used when nonpharmacologic measures provide insufficient pain relief and restoration of function. In the elderly, the most commonly used drugs are acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs--see Table 51-1). Acetaminophen is the first choice for pain relief because it is safer than NSAIDs and is effective. It can be prescribed in increasing doses up to 1 g qid (not to exceed 4 g/day) in most patients. Acetaminophen should be used cautiously in patients with liver disease and in those who consume > 2 alcoholic drinks per day because of the increased risk of hepatotoxicity.

For patients who do not adequately respond to acetaminophen, an NSAID should be considered. All NSAIDs appear to be equally effective, but patient responses vary, and several NSAIDs may be tried before relief is obtained. The therapeutic effects of NSAIDs are due to the inhibition of cyclooxygenase (COX), which is required for the synthesis of prostaglandins.

Two COX isoforms exist: COX-1 is expressed in most tissues, including gastric mucosa, and COX-2 is induced in inflammatory cells and synovium during inflammation. COX-2 is also found in the kidney but not in platelets. Most NSAIDs inhibit both COX-1 and COX-2, but newer selective COX-2 inhibitors affect only the COX-2 isoform and therefore cause less gastric irritation and ulceration and do not inhibit platelets. However, one of the COX-2 inhibitors, rofecoxib (withdrawn from market), appears to increase the risk of cardiovascular events after long-term use. The risk of cardiovascular events with other COX-2 inhibitors is undergoing evaluation.

The major adverse effects of older NSAIDs are similar, although the incidence varies by drug and among groups of patients. The most common adverse effect is gastrointestinal upset, which often occurs without evidence of ulceration or bleeding and may require discontinuation of the drug. However, ulceration and gastrointestinal bleeding can occur with all nonselective NSAIDs and are related to dose and frequency of use, but they do not correlate with symptoms, and bleeding can occur without warning. The relative risk for persons > 65 is three to four times greater than that for middle-aged persons. Taking nonselective NSAIDs with food may help minimize gastrointestinal symptoms, and concomitant use of cytoprotective drugs, such as the prostaglandin misoprostol or proton pump inhibitors, may decrease the incidence of ulcers in high-risk patients.

Older NSAIDs and the newer COX-2 inhibitors can impair renal function and cause sodium and water retention; they should be used cautiously in the elderly, particularly in those who have underlying renal disease, heart failure, volume depletion, or liver disease. Rare toxic effects in the elderly include cognitive dysfunction and personality changes.

In general, indomethacin should not be used as first-line therapy because, compared with other NSAIDs, it has greater toxicity and higher rates of progression of joint space narrowing, as seen on x-ray. It also produces more central nervous system adverse effects. Nonacetylated salicylates may have less renal toxicity and fewer antiplatelet effects than do other NSAIDs, but they are generally less effective.

When necessary, opioid analgesics can be used if they improve function and quality of life. However, given the chronic nature of osteoarthritis, prolonged use of opioid analgesics often causes problems with physical dependency. Sedation and nausea are usually transient with opioids. Constipation may be managed with stimulants or osmotic laxatives.

Intra-articular corticosteroids are indicated for symptomatic large joints unresponsive to the usual treatments. A joint should not be injected more than twice in a 2-week period. Triamcinolone is recommended. Systemic corticosteroids should not be used.

Weekly hyaluronic acid injections for 3 to 5 weeks improve symptoms of osteoarthritis of the knee. Patients > 60 with moderate to severe disease are most likely to benefit from hyaluronic acid.

Topical creams (eg, capsaicin or an NSAID) can be helpful as monotherapy or combined with oral analgesics, especially in patients with osteoarthritis of the hands or knees.

A combination of glucosamine sulfate with chondroitin sulfate is available in the USA as a nutritional supplement. Several studies have shown that 500 mg tid is more effective than placebo in relieving pain, but ongoing clinical trials should clarify the role of glucosamine in the treatment of osteoarthritis. This supplement has few adverse effects.

Surgery: Total arthroplasty is highly effective for treating osteoarthritis of the hip and knee, and age alone is not a contraindication. However, treatment goals (eg, pain relief, improved physical function) and the needs and capabilities of the patient must be clearly defined.

Arthroscopy with lavage is useful for osteoarthritis of the knee in patients who do not respond to pharmacologic treatment. The long-term benefits of arthroscopic lavage are unknown. Arthroscopy may also be used for diagnosis and treatment of internal derangements, such as a torn meniscus.