Clinical Evidence Concise
A Publication of BMJ Publishing Group
Osteoarthritis of the Knee
Am Fam Physician. 2008 Apr 15;77(8):1149-1150.
Osteoarthritis of the knee affects about 10 percent of adults older than 60 years, with an increased risk in those who are obese and have joint damage or abnormalities.
Progression of disease on radiography is common, but radiography changes do not correlate well with clinical symptoms.
We do not know the long-term effectiveness of nonsurgical treatments in reducing pain and improving function.
Exercise and physical therapy and joint bracing or taping reduce pain and disability in persons with knee osteoarthritis, but we do not know whether patient education or insoles are beneficial.
Oral and topical nonsteroidal anti-inflammatory drugs (NSAIDs) reduce pain in the short term compared with placebo, but they can cause gastrointestinal, renal, and cardiac adverse effects.
Paracetamol reduces pain in the short term compared with placebo, but may be less effective than NSAIDs.
Opioid analgesics reduce pain in patients with knee osteoarthritis, but they are associated with serious adverse effects and are not recommended for first-line treatment.
Intra-articular corticosteroids and hyaluronan may improve pain, although most studies are of poor quality.
We do not know whether acupuncture, capsaicin, glucosamine, or oral or intramuscular chondroitin improve symptoms in patients with knee osteoarthritis.
Consensus is that total knee replacement is the most clinically effective treatment for severe osteoarthritis of the knee.
Unicompartmental knee replacement may be more effective in the long term than tricompartmental knee replacement.
Tibial osteotomy may be as effective as unicompartmental knee replacement in reducing symptoms of medial compartment knee osteoarthritis.
What are the effects of nonsurgical treatments for osteoarthritis of the knee?
Exercise and physical therapy (pain relief and improved function)
NSAIDs (oral) for short-term pain relief
Likely to be beneficial
Corticosteroids (intra-articular) for short-term pain relief
NSAIDs (topical) for short-term pain relief
Simple oral analgesics for short-term pain relief only
Trade-off between benefits and harms
Education (to aid self-management)
What are the effects of surgical treatments for osteoarthritis of the knee?
Likely to be beneficial
NSAID = nonsteroidal anti-inflammatory drug.
Osteoarthritis is a heterogeneous condition for which the prevalence, risk factors, clinical manifestations, and prognosis vary according to which joints are affected. The condition most commonly affects knees, hips, hands, and spinal apophyseal joints. It is characterized by focal areas of damage to the cartilage surfaces of synovial joints and is associated with remodeling of the underlying bone and mild synovitis. Osteoarthritis is variously defined by a number of clinical and radiologic features. Clinical features include pain, bony tenderness, and crepitus. When severe, there is often a characteristic joint-space narrowing and osteophyte formation, with visible subchondral bone changes on radiography. Osteoarthritis of the knee is common, causes considerable pain and frequent instability, and, consequently, often results in physical disability. Radiography changes are not strongly associated with disability.
Incidence and Prevalence
Osteoarthritis is a common and important cause of pain and disability in older adults. Radiographic features in at least some joints are practically universal in persons older than 60 years, but significant clinical disease probably affects 10 to 20 percent of persons. Knee disease is about twice as prevalent as hip disease in persons older than 60 years (about 10 percent knee versus 5 percent hip). In a general practice setting, 1 percent of persons older than 45 years have a currently recorded clinical diagnosis of knee osteoarthritis; 5 percent will have had a clinical diagnosis at some point. A community-based cohort study showed that radiologic features of knee osteoarthritis were very common: 13 percent of women 45 to 65 years of age developed new knee osteophytes—an incidence of 3 percent per year.
Etiology and Risk Factors
Risk factors for osteoarthritis include abnormalities in joint shape, injury, and previous joint inflammation. Obesity is a major risk factor for osteoarthritis of the knee. Genetic factors modulate obesity and other risks.
The natural history of osteoarthritis of the knee is poorly understood. Radiologic progression is common, with 25 percent of osteoarthritic knees with initially normal joint space showing major damage after 10 years, although radiography progression is not related to clinical features. Persons with peripheral joint osteoarthritis of sufficient severity to lead to hospital referral have generally poor outcomes, with high levels of physical disability, anxiety, and depression. These patients also have high levels of health care resource use, including joint replacement, drugs, and walking aids.
editor's note: Paracetamol is called acetaminophen in the United States.
search date: October 2006
Adapted with permission from Scott D, Kowalczyk A. Osteoarthritis of the knee. Clin Evid Handbook. December 2007:389–390. Please visit http://www.clinicalevidence.bmj.com for full text and references.
This is one in a series of chapters excerpted from the Clinical Evidence Handbook, published by the BMJ Publishing Group, London, U.K. The medical information contained herein is the most accurate available at the date of publication. More updated and comprehensive information on this topic may be available in future print editions of the Clinical Evidence Handbook, as well as online at http://www.clinicalevidence.bmj.com (subscription required). Those who receive a complimentary print copy of the Clinical Evidence Handbook from United Health Foundation can gain complimentary online access by registering on the Web site using the ISBN number of their book.
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