Mechanisms of Action of Exercise Therapy for Knee OA

This week the GCU Physio Journal Club reviewed an article related to the benefits of exercise therapy for people with knee osteoarthritis (OA):

Improvement in upper leg muscle strength underlies beneficial effects of exercise therapy in knee osteoarthritis: secondary analysis from a randomised controlled trial.

Posted by Scott Rooney and Chris Seenan on behalf of the GCU Physio Journal Club

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Here is what we thought:

Osteoarthritis is a common cause of knee pain which can impact a person’s ability to perform their normal daily tasks. Exercise therapy is proven to be effective in managing the symptoms of knee osteoarthritis. However, the underlying mechanism associated with these benefits is unknown.

A team of researchers sought to explore whether changes in muscle strength and proprioception were associated with improvement in knee osteoarthritis symptoms. This post explores what the researchers did and what they found.

 

Methods:

Researchers analysed data from a randomised controlled trial which examined the effect of two exercise programmes. This trial included 159 participants with knee osteoarthritis who received strength training or strength training plus stabilisation exercises. Each group completed a 12-week exercise programme comprising of two 60 minute sessions each week at a rehabilitation centre in The Netherlands, and five days home-exercise.

Pain (numeric rating scale), activity limitations (WOMAC and get-up-and-go test), upper leg muscle strength (isokinetic dynamometer), and knee joint proprioception (detection of onset of passive movement) were measured at 6 weeks (mid-treatment), 12 weeks (post-treatment), and 38 weeks (6-month follow-up).

Results were combined and analysed to examine the relationships between changes in muscle strength and proprioception with pain and activity limitation while taking into account potential confounding factors (gender, age, duration of symptoms, use of pain medication, pain severity, BMI and knee malalignment).

 

Findings: 

At 6 months follow-up:

  • Pain
    • NRS scores improved by 34%
  • Activity limitation
    • WOMAC scores improved by 30%
    • Get-up-and-go test performance improved by 8%
  • Upper leg muscle strength improved by 23%
  • Knee joint proprioception improved by 36%
  • Significant association were found between change in upper leg strength and improvements in pain and activity limitations.
    • Change in muscle strength accounted for 7%, 6%, and 12% change in pain, WOMAC, and get-up-and-go test respectively.
  • No association was found between change in proprioception and any of the outcome measures

 

Authors conclusions: 

“this study provides evidence that upper leg muscle strengthening (of both quadriceps and hamstrings) is one of the mechanisms underlying the beneficial effects of exercise therapy in patients with knee osteoarthritis. Improved knee joint proprioception was not found to be related to the outcomes of exercise therapy.” 

Increases in strength of hamstrings and quadriceps muscle groups linked to reductions in pain and activity limitations.

 

GCU Physio’s opinion: 

We know that exercise therapy is effective for decreasing pain and increasing function in people with knee osteoarthritis. This high quality study provides an insight into the possible reasons for these effects and suggests that muscle strength is an important component. This has clinical implications in the planning and goal setting with of exercise interventions.

The main limitations of this study are the secondary nature of the analysis, the limited generalisation of the results due to specific knee OA sample studied and the possible limited validity of the proprioception outcome measure used.

 

Links: 

KNOOP, J. et al, 2015. Improvement in upper leg muscle strength underlies beneficial effects of exercise therapy in knee osteoarthritis: secondary analysis from a randomised controlled trial. Physiotherapy. 101, pp. 171-177.

Exercise and Arthritis from the Arthritis Research UK

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