Good Reasons Not to Avoid Exercising a "Bad Knee"

June 17, 2014

Are your patients with knee osteoarthritis quietly avoiding exercise, fearing it will worsen their pain? A new randomized trial shows they are mistaken: It eases pain. Another trial shows how much walking helps -- literally how much.

Holla JF, van der Leeden M, Knol DL, et al., Predictors and outcome of pain-related avoidance of activities in persons with early symptomatic knee osteoarthritis: A 5-year follow-up study. Arthritis Care Res (2014) Jun 6. doi: 10.1002/acr.22381. [Epub ahead of print].

Henriksen M, Klokker L, Graven-Nielsen T, et al., Exercise therapy reduces pain sensitivity in patients with knee osteoarthritis: A randomized controlled trial.Arthritis Care Res (2014) Jun 6. doi: 10.1002/acr.22375. [Epub ahead of print]

White DK, Tudor-Locke C, Zhang C et al., Daily walking and the risk of incident functional limitation in knee OA: An observational study. Arthritis Care Res (2014) Jun 12. doi: 10.1002/acr.22362. [Accepted article].

Are your patients with knee OA quietly avoiding exercise (whatever you say about it) because they fear it will make their pain worse? You can now tell them that research shows they are mistaken: The first randomized trial on the question finds the opposite to be true. Exercise lessens pain.

And when you say that walking is a good exercise for bad knees, you can also suggest a goal. A multi-center study shows that walking 60,000 or more steps per day improves function in knee OA over a two-year period.

A Dutch study of 828 people with early symptomatic knee OA found that knee pain, lack of energy, difficulty in performing activities like climbing stairs, and fear of pain with continued activity predict activity avoidance over time. Other predictors included a higher body mass index, co-morbid conditions, and joint damage seen on X-rays.

This kind of avoidance behavior starts a vicious cycle that results in deconditioning and muscle weakness, the authors point out, which leads to even more limitations over five years.

People with knee OA are indeed better served by engaging in appropriate physical activity such as a regular, structured exercise program, which a clinical trial from Denmark concludes should actually lessen pain.

Researchers from Copenhagen University randomly assigned 49 patients with early symptomatic knee OA to 12 weeks of supervised exercise three times a week or to a control group that did no exercise. At baseline and two and five years later, they tested pain sensitivity in the calf using a pressure cuff. Over time, the exercisers reported less pain and pain sensitivity when the pressure cuff was tightened.

The mechanism for this is unclear. Previous studies suggest that inflammation in OA may cause increased sensitivity to pain in the knee and nearby areas of the leg, say the Danish researchers. In addition to dampening inflammation, exercise may also enhance endogenous opioid and non-opioid pain relief.

Researchers at Boston University and Tufts University found that walking 6,000 or more steps per day may be all it takes to improve function in knee OA over two years -- and the more steps taken, the better the outcome.

Among the 1,788 participants recruited from the Birmingham, Alabama and Iowa City, Iowa areas as part of the Multicenter Osteoarthritis Study, 60% were overweight women with a mean age of 67.

Those who walked at least 6,000 steps a day not only staved off physical limitations over a two-year period, but each additional 1,000 steps taken per day yielded a 16% to 18% reduction in functional limitations.

The study, published online in Arthritis Care & Research, suggests that a good starting point for physical activity would be 3,000 steps a day -- an attainable goal for any older adults with or at risk of knee OA.

And the Dutch researchers recommend monitoring people with knee OA for avoidance behavior early on, in order to stop the vicious function-limiting cycle before it starts.