Osteoarthritis Dr D W Allen M.B,B.S, F.R.A.C.G.P.



Osteoarthritis (OA), by far the most common form of arthritis, is a degeneration of the smooth slippery and somewhat spongy layer of joint cartilage. OA can involve any joint in the body, most commonly the knee joint in women, the hip joint in men (especially in farmers and truck drivers), the small joints in the hands, wrists and feet, and the facet joints in the spine (where it is called spondylosis).

Do joints wear out or ‘rust’ out?

Joint cartilage has no blood supply and depends for nourishment on joint fluid produced by the synovial membrane surrounding the joint. As the joint moves under load, the cartilage is alternately compressed, squeezing out old fluid and waste products, and then decompressed, sucking in fresh nutrient-rich fluid. If a joint doesn’t move often enough through its full range of motion, that cartilage becomes undernourished and toxic. It can lose up to 16% of its thickness due to dehydration within just a few hours of immobility, then recovers with just 5-10 minutes of appropriate activity. It takes many weeks of regular activity for cartilage to recover from prolonged immobility – e.g. in a cast.

If a joint has been immobile for many hours and then subjected to sudden overload, the shock may not be fully absorbed by the dehydrated and thinner cartilage, resulting in microfractures in the underlying bone. These microfractures heal with more solid bone, seen on x-rays as subchondral sclerosis or hardening. Because this dense subchondral bone is less pliable, subsequent shocks to the joint can more easily damage the overlying cartilage. As the surface of the cartilage becomes roughened, friction increases, accelerating wear, erosions and loss of cartilage in OA.

Use it or lose it!
Inactivity followed by inappropriate activity is thus a major cause of OA, and physical activity is the single most important prevention and remedy. Even low-intensity activity, just moving the joint, is beneficial. Little and often is the key. When sitting for long periods, flex and straighten your ankles and knees (pulling the toes up and tightening the quads), then flex and rotate your thighs/hips at least six times every 20-30 minutes. Frequently move your arms, head and upper body. Get up and walk for a few minutes at least every hour, more often if you can. This can also nearly double the number of calories you burn and thus reduce overloading of your joints.

The body weight is amplified fourfold at the hip and sixfold at the knee when walking briskly on a hard surface. If you are overweight, it is therefore especially important to do light ‘warm up’ activities for a few minutes before subjecting weight-bearing joints to such stresses. Good cushioning shoes are also essential. Walking on level grass or soft sand is also easier on the knees. Cycling (e.g. an exercise bike) is great for the knees and water aerobics is kind on the hips and back, especially for overweight people with arthritis who find walking painful.

Where possible, avoid sustained pressure on a non-moving joint – e.g. standing still, holding or gripping an object. Keep the joints moving whenever possible, and regularly put all your joints through their full range of movement. Combine aerobic activity with strengthening activities. Tai chi and yoga have been shown to be beneficial, as has Jacobson relaxation exercises (alternately contracting and relaxing various muscle groups in turn).

Diet
Obesity is a major factor in causing OA of the knees and hips. Apart from its impact on weight-bearing joints, nutritional factors may also affect the integrity of joint cartilage and subchondral bone.

Fruit, vegetables and vitamin C. The Framingham Osteoarthritis Cohort Study (Arthritis and Rheumatism 1996; 39:648-56) demonstrated less pain and a threefold reduction in the progression of OA of the knee in those with a high vitamin C intake from fruit and vegetables, and another recent study showed those with OA of many joints had a low vitamin C intake from fruit and vegetables (Annals of the Rheumatic Diseases 2004; 63:843-47).

Folic acid and B vitamins. A study published in the Journal of the American College of Nutrition (1994) showed folic acid (6.4mg) and vitamin B12 (0.02mg) daily for two months to be more effective than anti-inflammatory drugs for OA of the hands. Another study of 72 patients with OA found that niacinamide (B3) 50mg six times a day for 12 weeks demonstrated a 30% improvement in joint pain and stiffness while those on placebo got 10% worse (Inflammation Research 1996;45(7):330-34).

Avocado and soy bean unsaponifiables were shown to have promising results in two studies (Cochrane Review 2000; Issue 4).

Marine Lipids. Our Western diet is high in pro-inflammatory arachidonic acid and omega-6 fatty acids from red meat and low in eicosapentaenoic acid (EPA) and omega-3 fatty acids from fish, especially herring and sardines. Lyprinol, an extract from the NZ green-lipped mussel rich in omega-3 fatty acids, significantly improved OA of the hip and knee over two months (Allergy and Immunology 2003; 35(6):212-6).

Glucosamine Sulphate. A Cochrane Review of 20 studies (2005, issue 2) found glucosamine to be 28% better than placebo for pain and 21% better for function. It was as effective as anti-inflammatory drugs, but took longer to work (3-6 weeks for pain relief). It is the only substance so far shown to slow progression of cartilage degeneration in OA, demonstrated in several 3-year trials. There are many brands of this shellfish extract, but the Rotta preparation has been most extensively studied and found to be superior. The dose used in most studies was 500mg three times a day, though some used 1,000mg twice daily with comparable results. It appears to be equally effective when applied topically (as Arthro-Aid Direct cream) twice daily to knees, hands or feet (but not to deep joints such as hips) and benefits can usually be experienced within days.

Chondroitin Sulphate. Like glucosamine, this substance is also incorporated into the proteoglycan matrix of cartilage and is often combined with it (e.g. Osteo-Eze). Although not as well studied as glucosamine, one study showed it to be as effective as diclofenac (Voltaren) in improving pain and mobility in OA. It took longer to take effect but, unlike Voltaren, benefits continued for three months after it was discontinued (Journal of Rheumatology 1996; 23(8): 1385-91).

Herbs. While many fruits, vegetables, herbs and spices contain natural salicylates, the richest source (from which aspirin was originally derived) is Salix alba or white willow bark. A two-week study of willow bark containing 240mg of salicin resulted in 14% pain reduction, compared to a 2% increase on placebo (Rheumatology 2000; 59(5):314-20). Another study showed Devil’s Claw to be as effective as (and much safer than Vioxx) in relieving low back pain (Rheumatology 2003; 42:141-48). Ginger, turmeric and feverfew may also be helpful.

Paracetamol. Panadol Osteo / Panamax / Dymadon (two tablets three times a day) has been shown to be at least as effective for pain-relief as any anti-inflammatory drug or NSAID (e.g. Celebrex, Mobic, Voltaren etc.) and much safer. NSAIDs often increase blood pressure and the risk of heart attack, impaired renal function and gastrointestinal haemorrhage. They do nothing to slow the progression of OA, and may actually increase cartilage degeneration. They should only be taken when all else fails to give adequate pain relief.

Heat and massage can often help to relieve pain and may increase blood flow to the synovium.

Acupuncture and aquapuncture (injections of sterile water around joints) have been shown to relieve the pain of OA in many cases.

Joint injections with either cortisone (Celestone) or Synvisc have been shown to be safe and effective in the knee. Synvisc, an artificial joint fluid, is much more expensive and takes longer to work, but is more effective long term.

Joint replacements provide the most cost-effective treatment for advanced OA of the hip and knee.