Effects of strength training on the incidence and progression of knee osteoarthritis.

Mikesky AE, Mazzuca SA, Brandt KD, Perkins SM, Damush T and Lane, KA. Arthritis and Rheumatism (Arthritis Care and Research). 2006;55(5):690-699.

This is the editor's interpretation of a paper published in the orthopaedic literature in 2006 - our attempt to make relevant medical articles accessible to lay readers. If you wish to read the original it is easy to ask your librarian to obtain a reprint for you from any medical library.

The authors of this paper noted that several previous researchers had confirmed that exercise regimes improved symptoms in patients with knee osteoarthritis (OA). They also noted that more than 22 million American adults (25-74 years) suffer from OA of the knee and it leads to a progressive deterioration in one's ability to perform normal daily activities. The risk of OA is associated with increasing age, the female sex, obesity and pre-existing quadriceps weakness.

In this study they set out to evaluate whether quads strengthening exercises would prevent the radiographic changes one normally sees with OA or whether it would slow the progression of the problem. 221 functionally independent adults aged 55 or more were included in the study, which was conducted over a 30 month period. Some had OA and some did not; some had pain and some did not. The people in the study were stratified into four groups:

  • OA plus pain
  • OA with no pain
  • No OA but with pain
  • No OA and no pain

The individuals were randomly assigned to receive either strength training or simply range of motion (ROM) exercises. Both groups were permitted to continue their usual painkillers and anti-inflammatory medicines during the trial.

At the begininng of the programme and then every six months the entrants were evaluated in respect of their muscle strength, knee pain, knee function and their general health status.

The authors have given in the paper details of the strength training programme and the interested reader can refer to the original paper.


There was a high fallout rate - 31% pulled out of the study, mostly because of the burden of participation, and the travel and time constraints. Only one person discontinued the trial because of an increase in pain related to the strength training.

Both groups showed some reluctance in the first 12 weeks, with only half the number of scheduled attendances. Attendances improved over the following 18 months.

The classic form of isotonic exercise is lifting free weights. Isokinetic exercise uses a machine like a KinCom where the speed of muscle contraction is controlled.

The outcome of the strength training was somewhat confusing. Two elements of muscle strength were tested - isotonic strength and isokinetic strength. There were overall gains in isotonic strength but no gain in isokinetic strength - the authors put this down to the exercise regime being biased towards isotonic exercise. Subjects in both groups lost lower-extremity strength over the 30 month period but the rate of loss was slower with the strength-training group than the ROM group.

Equally the strength training did not significantly affect the rate of joint space narrowing in the subjects with OA. In fact it looks as if the strength training actually seems to have harmed the knee in those people who did not have OA, as they showed a greater rate of joint space narrowing than would have been predicted. The incidence of osteophytes (spurs) demonstrable on X-ray did not appear to be affected by the strength training either.

Another confounding feature is that the pain scores also did not change significantly in any of the four groups.