Below is the main supplement commonly recommended for knee arthritis treatment. You can find it online or in local shops.

Avocado-soybean unsaponifiables (ASU)

What it is: An extract from avocado and soybean oil.

Beneficial effects: It reduces the pain and inflammation associated with OA, slows down cartilage degeneration and promotes cartilage repair.

How it works: The active ingredients are thought to be phytosterols (plant steroids), which have anti-inflammatory and painkilling properties and stimulate the production of collagen, a major component of joints, tendons, muscles and ligaments.

Evidence of effectiveness: In a study at Lapeyronie Teaching Hospital in France in 2009, participants with OA in the hip or knee took a supplement containing 300 mg or 600 mg of ASU. After six weeks, just 43 per cent of people taking the supplement needed to use anti-inflammatory drugs, compared to almost 70 per cent of the control group. Those taking the supplement also had better movement. In 2008, a review of the combined results of four trials lasting three to 12 months showed that twice as many OA sufferers taking 300 mg of ASU reported an improvement in their symptoms as those given a placebo. ASU was effective in reducing not only the pain, but also problems with walking and carrying out everyday tasks. Participants with OA of the knee appeared to gain the most relief.

Safety: No major side effects have been reported, though some users have experienced stomach upsets and minor allergic reactions; people who are allergic to chestnuts or bananas are advised not to take ASU. At present, supplements containing ASU are not available in the UK, but they can be bought online from the US (see Useful Products). Taking avocado and soybean oils themselves wouldn’t offer the same benefits because, even in large amounts they don’t contain enough of the active ingredients to provide a therapeutic effect.