Credit for Learning: 2This article will form the basis of questions under the PJ/College of Pharmacy Practice Credit for Learning scheme |
Osteoarthritis affects around 12 per cent of people over 65 years old and it is the most important rheumatological cause of disability. This article discusses the disease and its treatment
Osteoarthritis is a predominantly non-inflammatory abnormality of the synovial joints which is characterised by cartilage loss and an accompanying bone response. It occurs most commonly in the hands, knees, spine and hips. The symptoms include joint pain, stiffness, limitation of movement and swelling. Osteoarthritis, like rheumatoid arthritis, is more common in women than men and, overall, affects 2.5 per cent of the population. This percentage increases with advancing age such that osteoarthritis is the most common chronic joint condition in individuals aged over 65, where it affects approximately 12 per cent of the population.1 For this reason, osteoarthritis is the single most important rheumatological cause of disability and it poses a significant challenge to health care. In this article, the pathogenesis, clinical presentation and management of osteoarthritis are reviewed.
The specific aetiological factors are unknown, but a number of genetic, patient specific and environmental risk factors have been implicated in the development of osteoarthritis. Although an inherited defect in type II collagen metabolism is described in families with premature onset polyarticular osteoarthritis (this is rare), the genetics of common osteoarthritis still require further study.2
Patient specific factors include obesity, female gender and increasing age. Environmental factors include abnormal joint loading during occupations involving repetitive use of joints over prolonged periods.1 A detailed description of the structural and biochemical changes occurring in osteoarthritis and the accompanying radiographic features is provided in the literature.2,3
The most frequent presenting feature of osteoarthritis is pain which is worsened by movement, eased by rest and tends to be worse at the end of the day. Morning stiffness is also common; unlike that experienced by rheumatoid arthritis sufferers, this usually lasts less than 30 minutes. Patients may also complain of a sensation of creaking and cracking (or crepitus) in the joints, which is related to movement.4
Swelling of osteoarthritic joints may be caused by synovitis with effusion or osteophyte formation (abnormal bony outgrowth) at the joint margins. The bony enlargement of osteophyte formation may also give rise to visible joint deformity.
In advanced osteoarthritis, the articular cartilage is lost, the subchondral bone collapses and secondary osteophyte formation fails to support the joint. The result is a deformed, poorly functioning, painful joint which is unstable in some patients.3 Loss of function of the joint may be caused by pain, swelling, deformity or a combination of these factors. In addition to these physical problems, anxiety and depression are also commonly associated with osteoarthritis. Their severity tends to be related to the degree of pain experienced by the patient.
Osteoarthritis most commonly affects the knees, hands (the first carpometacarpal, distal and proximal interphalangeal joints) and the lumbar and cervical spine. The hip is less commonly affected and the least common sites are the ankle, wrist, elbow, shoulder and the metacarpophalangeal joints of the hand.
The pattern of joints involved varies between the sexes. Men suffer more hip disease. Women experience more severe and polyarticular disease,4 for example, a man may have one knee affected, but a woman may suffer in both knees, a hip and some fingers. The degree of disability also depends on the site involved. For example, pain and deformity at weight-bearing joints, such as the hip or knee, may immobilise the patient, whereas similar changes in the interphalangeal joints of the hand cause less functional impairment.3
The aims of osteoarthritis management are primarily to reduce pain, but also to optimise mobility, avoid or minimise joint deformity and to educate the patient about their disease. The therapeutic options available to realise these goals are limited. Drug therapy consists of simple analgesics, topical or oral non-steroidal anti-inflammatory agents and local corticosteroid injections. These can be combined with non-drug measures such as weight reduction in obese patients, physiotherapy and/or surgery. Successful management depends on a "total patient" approach in which the following factors are considered:
Biomechanical factorsIt is well documented that weight reduction significantly affects the risk of developing osteoarthritis and that obesity is associated with symptomatic disease. Therefore, patients who are overweight should be encouraged to lose weight so as to reduce stress on their joints and to increase their mobility. This strategy is particularly beneficial in patients with osteoarthritis of the knee.
Physiotherapists contribute significantly to management by advising on exercises tailored to the patient's needs, which help to preserve the function of the joint, as well as protect it from further damage. In addition, physiotherapists can identify activities in the individual's home routine that stress joints unduly (for example, bending or lifting). Cessation or modification of these activities can produce considerable pain relief.
Physiotherapy can also help patients regain muscle strength around weakened joints, improve the range of movement of affected joints and enhance general wellbeing. Patients should be encouraged to remain active, using a "little and often" approach to exercise, within reasonable limits. Swimming, which allows the patient to work their arthritic knees or hips without impact loading, is considered to be very beneficial. Physiotherapists can also assess the need for mobility aids and provide training on their use.
Occupational therapists have an imporant role to play in advising patients on how to protect their joints from further damage. They can provide a range of devices that can be used in the home to assist with the activities of daily living, such as personal hygiene, dressing and household chores. A number of aids, ranging from long-handled combs and shoe-horns to special cutlery, bath and shower aids and toilet rails, are available. In addition, resting splints can be used to maintain the position of joints to prevent deformities developing and dynamic splints can be used to brace unstable joints to allow movement with stability.2
Psychological factors The patient's psychological status has been demonstrated to be an important determinant of symptomatic and functional outcome in osteoarthritis. Therefore, it is vital that patients are given a clear explanation of the nature of their disease, methods of management and likely prognosis as soon as osteoarthritis is diagnosed. This will help them to come to terms with the disease, understand how it will affect their life and how they can work with health care professionals to manage their condition. Providing social contact and access to telephone helplines allows patients to discuss their disease (with other patients, therapists and support groups) and share experiences, which can also effectively improve symptoms.
In addition, some therapists, eg, clinical psychologists and occupational therapists, practise relaxation techniques to help improve pain control and enhance the patient's wellbeing. The Arthritis and Rheumatism Council (ARC) provides a number of information leaflets to support patients with osteoarthritis.
Simple analgesics Pain is the main reason why patients with osteoarthritis seek help from health care professionals. However, drug treatment is an adjunct, not a substitute for other types of treatment. As osteoarthritis has only a minor inflammatory component, paracetamol is now accepted as first-line therapy in uncomplicated osteoarthritis. It can be taken in a regular full dosage (up to 4g per day) or on an "as required" basis.
The effect of compound analgesics, which are commonly prescribed for osteoarthritis, is often disappointing as many contain sub-therapeutic doses of opioids. However, preparations with a full dose of the opioid component often cause unwanted side effects, such as constipation, especially in elderly patients. Analgesics such as co-proxamol are generally thought to be no more effective than paracetamol alone and are probably best avoided as they may be particularly hazardous in overdose.
Oral non-steroidal anti-inflammatory drugs (NSAIDs)Osteoarthritis is primarily a non-inflammatory disease. Few studies have been carried out to compare the efficacy of NSAIDs with simple analgesics in osteoarthritis, but NSAIDs are frequently prescribed. It has been suggested that the efficacy of NSAIDs in osteoarthritis relates to their action as analgesics and not as anti-inflammatory drugs.4 NSAIDs should be reserved for patients whose symptoms are not controlled by other means, or to manage acute exacerbations that are associated with inflammation.
If it is necessary to use an NSAID to manage osteoarthritis, the following points should be borne in mind. As published studies have failed to identify a difference in the relative efficacy of different NSAIDs, individual choice should be based on relative safety, patient acceptability and cost. Therefore, ibuprofen should be used first line because of its good safety profile and low cost. Secondly, not all NSAIDs are licensed to treat osteoarthritis. For example, because of its high level of side effects, azapropazone is no longer licensed for osteoarthritis and meloxicam is only licensed for short-term treatment of acute exacerbations. Thirdly, the usefulness of NSAIDs is limited by their side effects. These can be a particular problem in the elderly or in those with poor renal function. If it is absolutely essential to use an NSAID in an elderly patient, or in a patient with a previous history of peptic ulceration, the concurrent administration of an H2 antagonist, misoprostol or a proton pump inhibitor should always be considered.
In patients with renal insufficiency, NSAIDs should be avoided whenever possible or used in very low doses if the benefits are expected to outweigh the risks. In such cases, serum creatinine, urea and electrolytes must be monitored regularly.
Topical NSAIDs A wide range of topical NSAIDs are available in a variety of formulations, such as gels, foams, creams, ointments and sprays. These products are promoted on the basis that they diffuse rapidly and directly into joints. This is claimed to result in high local and low plasma concentrations of the drug and theoretically gives a lower risk of systemic side effects than oral NSAIDs.
Over the past few years there has been considerable debate about the safety and efficacy of topical NSAIDs. However, a recent systematic review of 86 trials involving over 10,000 patients showed that four topical NSAIDs (ketoprofen, felbinac, ibuprofen and piroxicam) were significantly more effective than placebo for pain relief and that this efficacy was not just related to a rubbing action. None of these NSAIDs appeared to be more effective than the others. In addition, there was no significant difference in the incidence of adverse drug reactions when topical NSAIDs were compared with placebo after two weeks' treatment for osteoarthritis.5 A randomised double-blind trial which compared piroxicam 0.5 per cent gel with oral ibuprofen 400mg three times daily showed no statistically or clinically significant difference between the two treatments.6The most common side effects of topical NSAIDs are cutaneous reactions, such as urticaria, pruritus, irritation and contact dermatitis. These occur in approximately 2 per cent of patients and tend to be self-limiting.7 However, as the incidence of these side effects was similar in treatment and placebo groups, they may be related to the composition of the vehicle rather than the NSAID component.
Published evidence suggests that topical, unlike oral, NSAIDs are associated with few systemic side effects as plasma concentrations are low compared to oral therapy, although the risk of systemic side effects is likely to increase if excessive quantities of topical NSAIDs are used. Hypersensitivity, asthma and renal toxicity have all been reported.1,7 In a post-marketing surveillance study of felbinac 3 per cent gel, 1 per cent of patients experienced dermatological side effects whereas 0.1 per cent experienced respiratory adverse events and 0.1 per cent experienced gastrointestinal side effects.8
As a clear role for topical NSAIDs in the treatment of osteoarthritis has yet to be defined, their routine use for this condition remains unjustified. However, they may be a safer alternative to oral NSAIDs in elderly patients who have an inflammatory component to their osteoarthritis. In the meantime, data are still needed to confirm their efficacy compared with simple analgesics, such as paracetamol, and topical rubifacients. If it is necessary to use a topical NSAID, then choice should be based on the cheapest available preparation.9
Intra-articular corticosteroidsSystemic corticosteroids have no role in the management of osteoarthritis. However, injections of intra-articular corticosteroids can be used successfully to reduce pain and relieve inflammation (synovitis) associated with acute flare-ups. They also have a place in treating patients awaiting surgery and in enabling patients with severe pain to participate more easily in an exercise programme. Corticosteroids may cause direct cartilage injury and accelerate cartilage loss and so repeated intra-articular injection is probably not justified. It is recommended that a joint should not be injected more frequently than every three months.4 As there is no evidence for differences in efficacy between different intra-articular corticosteroids, selection relates to the prescriber's preference. The appropriate dose will vary with the joint involved and the corticosteroid used. For example, an intra-articular dose of methylprednisolone acetate ranges from 4 to 10mg for a small joint to 20 to 80mg for a large joint (such as the knee), depending on the volume of the effusion.
Chondroprotective agents The destruction of cartilage is one of the major processes of osteoarthritis progression. NSAIDs and other drugs have different in vitro actions on cartilage metabolism. There is speculation that some NSAIDs may be protective or even anabolic; this has been termed a "chondroprotective" action. However, evidence of any beneficial effect of NSAIDs on cartilage breakdown in clinical situations is lacking.4
Various other agents including chondroitin (glycosaminoglucuronglycan sulphate), glucosamine (chitosan) and vitamin E (tocopherol) have been examined for such activity. In a crossover study, tocopherol 600mg daily was more effective than placebo in relieving pain induced by osteoarthritis. Results showed that 52 per cent of the patients treated with vitamin E reported analgesia compared with 4 per cent on placebo.10
Chondroitin has also been shown to result in an improvement in pain and function in patients with osteoarthritis of the knee.11,12 Similarly, glucosamine has been reported to be effective in reducing the symptoms of osteoarthritis.13 Finally, regular injections of hyaluronic acid derivatives (weekly for three to five weeks) into the knee have shown some effects on pain.3
However, many of the trials with these agents have been in small numbers of patients, poorly designed and/or have failed to assess the long term safety and optimal dosing requirements. Therefore, further studies are warranted to assess if these agents have any chondroprotective action and to define their place, if any, in the mangement of osteoarthritis.3,13
Joint replacement has an important role in the management of pain, stiffness and deformity. Surgery is most commonly undertaken for the hip and knee, although various finger joints may also be replaced. Two surgical procedures for knee and hip disease are osteotomy and arthroplasty. Osteotomy (cutting or sectioning of bone) relieves pain and can stimulate fibro-cartilaginous healing of the joint. Arthroplasty (joint replacement) is increasingly successful and is used widely in end-stage hip and knee disease. Long-term results with both procedures are excellent in most centres. Surgery has greatly advanced management for patients with intractable pain and severe impairment of function as a result of end-stage osteoarthritis.
Application of local heat and cold treatment, ultrasound therapy, acupuncture, hydrotherapy and spa treatment are used commonly in osteoarthritis. There is evidence that these modalities may improve pain and are worth trying; however there are few well designed trials to support this hypothesis but the treatments have a strong "placebo" effect.
Management of osteoarthritis should involve a "total patient" approach in which pain severity, functional disability, the patient's expectations, the presence of anxiety or depression, synovitis, joint instability and the local and general condition of the muscles are all considered. Using this approach, paracetamol can often be combined successfully with non-drug measures, such as maintenance of optimal weight, general exercise, physiotherapy, use of biomechanical aids and/or surgery, to achieve a positive outcome in many patients. NSAIDs should be reserved for patients who do not respond to regular full doses of simple analgesics such as paracetamol.
Mrs Wood is deputy chief pharmacist at University Hospital, Liverpool
References1. Watson M. Management of patients with osteoarthritis. Pharm J 1997;259:296-7.
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