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Osteoarthritis: Most frequent joint disease in our society 

By Winthrop Professor Johannes Nossent, MD, PhD, FRACP, Rheumatology and Musculoskeletal Medicine, UWA

Joints form a connection between bones and are involved in every movement by the human body. Joints contain various tissues: bones as load bearing structure, articular cartilage as the cushioning for the bones, synovial lining membrane for production of joint lubrication fluid and a joint capsule plus ligaments for stability. Under normal conditions this effective system makes for joints that can withstand repetitive movements (up to a million times a year) and loads of up to six times body weight.

Osteoarthrosis (OA) develops as a non-inflammatory joint condition through a combination of cartilage degeneration, bony outgrowths and thickening of the joint lining. The terms Osteoarthrosis and Osteoarthritis are interchangeable. OA symptoms usually begin when focal lesions occur on the cartilage surface as a result of repetitive movements, overloading or trauma. This results in progressively painful movement and limitations in joint function. OA is often a generalised condition and can affect any joint, but hands, spine, hips and knees are preference spots for OA.

OA is by far the most frequent joint disease in our society and while numbers are not fully comparable, the frequency of symptomatic hand and knee OA in people over 16 years of age is around 6 % for each - with the numbers in WA rising to 50 % in the age group over 65.

There is no known cause for OA, but it is thought to result from an inter-play between a numbers of factors. These include fixed variables such as age, ethnicity and genetics as well as biomechanical factors, which are potentially responsive to prevention and/or intervention (e.g. trauma, body weight, abnormal load bearing, and muscle mass and bone density).

In mild arthrosis, only how to avoid progression may be needed. With more severe changes, measures to reduce load bearing such as supports (splints/cane, reducing weight) and pain medication may become needed. In severe cases, surgical interventions prove helpful including stiffening of the joint (arthrodesis) and corrective surgery to redistribute load or replacing (part-of) the joint.

Medical interventions such as the prolonged use of fish-oil, cartilage substitutes or the injection of synthetic joint lubricant have not been shown to improve disease outcome, but may provide symptomatic relief. Graded exercise and supportive treatment with hydrotherapy, occupational therapy and physiotherapy provide additional pain relief and increase muscle strength and joint stability.

There is a frustrating lack of causative treatment in OA. The most pressing issue is to find effective ways to get cartilage cells to grow back cartilage in affected joints, and thus stop disease progression. Over the last decade, research into OA has finally caught on, and also in WA. Clinical research efforts will focus on transplanting new cartilage grown in the laboratory or injecting stem cells to produce new cartilage cells.

Basic research needs to identify the modifiable risk factors for OA, such as genes that determine the amount and quality of cartilage formation, and come up with ways to influence these genes. OA is the one area of joint disease where a Nobel Prize is waiting for the breakthrough discovery!

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