Managing osteoarthritis of the knee
Authors: Domhnall MacAuley
Journal: BMJ (2004)

A slightly swollen and aching knee. Walking is difficult, the stairs are almost impossible, and so begins the downward spiral of inactivity, immobility, and weight gain. Osteoarthritis of the knee is a familiar picture, presenting usually when it is too painful to ignore but too early for surgery. Patients have often already made the diagnosis themselves and seek a solution. They want pain relief so they can walk, kneel, climb a ladder, shop, or simply get around in comfort. Most patients have tried paracetamol, hot water bottles, someone else's great new tablets, a cabbage leaf, various herbal or homoeopathic medications, prayer, copper bracelets, and many other remedies before asking for help. Most general practitioners would reach for the keyboard tapping out their favourite non-steroidal anti-inflammatory (NSAID).

NSAIDs do not seem to offer a long term solution. In a comprehensive systematic review and meta-analysis of randomised placebo controlled trials in this issue of the journal, we learn that NSAIDs can reduce short term pain only slightly better than placebo (p 1317).1 This study does not support the long term use of NSAIDs in osteoarthritis of the knee, and our prescriptions may, in fact, be doing harm. Good scientific reasons exist for this—prostaglandin inhibitors reduce the immediate inflammatory response in the acutely injured joint but may inhibit long term healing. Good medical reasons also exist—the gastrointestinal side effects are well known, but patients with osteoarthritis are older and the British National Formulary recommends that NSAIDs be used with caution in elderly people, who are more likely to have cardiac, hepatic, or renal impairment.2 The EULAR guidelines recommend both pharmacological and non-pharmacological measures but advise simple analgesia at first.w1 w2 Another recent systematic review concludes that paracetamol is an effective agent for relieving pain due to osteoarthritis and, although safer, is less effective than NSAIDs. They recommend paracetamol as a first line treatment for reasons of safety.3

What are the alternatives? An osteoarthritic knee is often a weak knee. Muscle dysfunction may be as important a cause as wear and tear.4 Physical training may relieve symptoms, and both strengthening and endurance exercise is of benefit to patients with mild and moderate osteoarthritis. Referral to exercise training appears to be the most useful option but home based programmes are effective too.5,6 Training improves muscle strength and joint mobility, but the condition is progressive and training offers only a temporary respite in the inevitable decline in function.7 Facilities for getting people started and providing support through a programme of exercise training are not commonly available in the United Kingdom so referral is rarely an option. Acupuncture may reduce pain and improve both physical function and health related quality of life.w3 Taping may also be a useful short term and intermittent intervention, although arranging weekly taping by a physiotherapist might prove difficult in the NHS.8 Topical anti-inflammatory applications are of some help, and patients often try glucosamine and chondroitin, which have been shown to be of benefit and can be sold directly to patients.9-11

Intra-articular injections are effective. Notable improvements are seen in the short term (two weeks), and in some longer term studies (16-24 weeks).12 But the short term benefits can be important. Normal lives are a patchwork of work, leisure, holidays, weddings, and other life events. Short term benefit from an intra-articular injection may give sufficient temporary improvement to allow a patient to go on holiday, take part in a family event, or simply enjoy getting outdoors during summer. The pain relief can be almost immediate and the improvement in mobility magical. The benefit, however short term, can make such a difference. No one knows the long term effects of repeated injections although they seem to be safe over two years. Surgery is ultimately the preferred option. But, for most patients the most difficult period is between onset of the symptoms and the point when surgery becomes necessary.

Thankfully, surgery does offer the ultimate answer in the severely osteoarthritic knee.w4 The results are good in about 90% of patients, with improvement in pain, functional status, and overall health related quality of life, and 85% of patients are satisfied with the outcome. The strongest evidence is in studies with two years' follow up, but the results are also positive in studies with five to 10 years' follow up. The overall complication rate of 5.5% includes infection, deep vein thrombosis, and poor wound healing and a further 0.5% die during surgery. The revision rate after five or more years is 2%.w5 Total knee replacement is a good option when other strategies fail, in patients with chronic pain and functional limitation.

The slightly swollen aching knee usually gets worse. We may slow the inevitable decline in function and provide short term symptomatic relief. Prescription medicines offer some benefit, but patients may be justified in self medication with glucosamine and chondroitin. Intra-articular injections do offer short term benefit and, although general practitioners have been reluctant to inject, perhaps improved training may encourage a more active approach. Exercise training, guided by a physiotherapist, may also delay decline.