Osteoarthritis (OA) is the most common form of arthritis and affects approximately 30 million Americans. OA develops as a result of breakdown of joint cartilage, the gristle that caps the ends of long bones. This cartilage loss then causes the bones to rub against each other, leading to stiffness, pain and loss of movement in the joint. The symptoms develop due to a combination of mechanical factors as well as local inflammation.

OA is a disease of weight-bearing joints and as a result causes a patient to have more trouble walking and climbing stairs. In fact, it's been estimated that more than 100,000 people with OA of the hip or knee can't move independently from their bed to the bathroom and need some form of assistance. This is a tragedy!

The treatment of osteoarthritis usually includes a combination of medication, weight control, physical therapy, injections, and exercise.

A special type of exercise therapy known as "pool therapy" or "hydrotherapy," has patients doing aerobic activities or stretching and strengthening and range of motion exercises, in water heated to about 90 to 97 degrees Fahrenheit.

A recent review of the efficacy of hydrotherapy was published in The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews allow evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic. (Bartels EM, et al. Aquatic exercise for the treatment of knee and hip osteoarthritis (Review). Cochrane Database of Systematic Reviews 2007, Issue 4).

[The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information].

The Cochrane reviewers looked at six trials that had 800 participants who all had OA. Four studies included patients with osteoarthritis of either the knee or hip, one study followed patients with only hip arthritis and one included patients with knee arthritis only.

In the studies, patients did aquatic exercises for different lengths of time and numbers of sessions per week and were compared to other patients who did no exercise or exercised on land. Most of the studies measured patients after three months of therapy.

Based on the studies' results, the reviewers said, "In people with osteoarthritis of the hip or knee, pain may decrease by 1 more point on a scale of 0 to 20 with aquatic exercise, and function may improve by 3 more points on a scale of 0 to 68."

"There is gold-level evidence that for osteoarthritis of the hip or knee, aquatic exercise probably slightly reduces pain and slightly improves function over three months," the reviewers wrote. "Based on this, one may consider using aquatic exercise as the first part of a longer exercise program for osteoarthritis patients."

The reviewers were unable to find evidence on whether aquatic exercise affected patients' walking ability or stiffness after treatment sessions.

The reviewers added that more research could help determine long-term effects and to understand which kinds of aquatic exercise as well as frequency and length might benefit osteoarthritis sufferers.

Author's note: Water exercise makes sense for OA because the buoyancy relieves stress on joints. It is the ultimate low impact workout. This is particularly important for those patients with OA who are overweight, which is, sadly, more common than not. The benefits that accrue to the patient include not only relief of pain and improved mobility but if done often enough should help with weight loss.

For those people who do not have access to a pool, other low impact activities such as a stationary bike or elliptical trainer might be beneficial.