Exercise in water for osteoarthritis of the lower limbs


This week the baby Elves were swimming in our local woodland swimming pool learning all about buoyancy. This reminded me that exercise in water – hydrotherapy or therapeutic aquatic exercise – is recommended to people with osteoarthritis because of the reduced loading on the joint as a result of buoyancy. But what is the evidence for this?

A recent systematic review examined the effect of therapeutic aquatic exercise on symptoms and function associated with lower limb osteoarthritis.

Here’s what they did

They searched 6 databases (MEDLINE, PubMed, CINAHL, SPORTDiscus, PEDro, and EMBASE) for studies with an RCT design and a control comparison group who continued usual care or participated in a sham intervention, and published in English.

Participants in included studies must have clinically diagnosed osteoarthritis (as assessed with radiography or according to American College of Rheumatology guidelines) in one or more joints of the lower limb, with no age or sex restrictions.

Therapeutic aquatic exercise was exercise involving full immersion of the body in water.

Quality of studies was assesed on the 11 point PEDro scale, studies with a PEDro score of 5, indicating low methodological quality and a high risk of bias were excluded. Outcome data had to be reported for at least one outcome at baseline and postintervention.

Data were extracted and checked for accuracy by 3 independent reviewers, results are reported as Standardized Mean Difference (SMD) with 95% confidence interval (95% CI).

Here’s what they found

  • 11 studies, involving 1,092 participants, were included in the qualitative and quantitative synthesis
  • Six studies included knee and hip, 3 studies only knee, 1 study only hip, and 1 study included any lower limb osteoarthritis.
  • Planned exercise dose varied from 100 minutes per week to 180 minutes per week for 6 weeks to 52 weeks (in total, from 9 to 107 hours). Frequency of treatment was either 2 or 3 times a week (2 times a week was most popular).
  • Effects directly after intervention
    • Pain: a small but significant effect  (SMD 0.26 [95% CI 0.11, 0.41])
    • Stiffness: a small but significant effect (SMD 0.20 [95% CI 0.03, 0.36])
    • Self-reported and objectively measured physical functioning: small but significant (SMD 0.30 [95% CI 0.18, 0.43] and SMD 0.22 [95% CI 0.07, 0.38], respectively)
    • Physical functioning at activity level (SMD 0.22 [95% CI 0.01, 0.42])
    • and ROM (SMD 0.56 [95% CI 0.14, 0.99])
    • Muscle strength: no significant effect
    • Quality of life: a small but significant effect (SMD0.24 [95% CI0.04, 0.45])
  • Effects at 3 and 6 month follow up: only 2 studies examined this but the effect had been lost at both follow-up measurement points.
  • Adverse events: were reported by 5 studies including increase in pain.

The authors concluded

Therapeutic Aquatic Exercise is effective in managing symptoms associated with lower limb osteoarthritis


Exercise in water can help people with lower limb osteoarthritis

The Musculoskeletal Elf’s view

The Musculoskeletal Elf

The authors of this review elected to use Standardised Mean Differences (SMD) rather than Mean Differences (MD) to report the effect sizes (ES). One advantage of using SMD is that it allows the statistical synthesis of different outcome measures, but the disadvantage is that it is difficult to interpret in a clinical situation.

Let’s see an example.

Measurements of pain are easy to understand when they are all measured using the same scale such as a Visual Analogue Scale (VAS) 0-100mm anchored with zero no pain and 100 maximum imaginable pain. The effect size is reported as a mean difference such as 20mm difference between the groups in favour of one intervention and 95% Confidence Intervals

But what about when studies use different scores, as they did in this review where pain was measured using; VAS (0-100), VAS (0-10), WOMAC pain (0-20) and KOOS pain (0-100)? Well they can still be combined and examined for differences using Standardised Mean Differences. However, this gives Effect Eizes in SMD which is pretty meaningless to most clinicians.

This is why there are organisations such as OMERACT and the COMET INITIATIVE who are advocating for the adoption of standardised or core outcome measures in future clinical trials and for clinical practice.

A very good point came up earlier today about the difficulty some people experience when doing waterbased exercise. See some questions below.

What do you think?

  • Do you recommend exercise in water for people with OA hip and knee?
  • Do you go to the pool to exercise?
  • Does your pool have special sessions with warmer water, easy access into the water and provision of additional floats etc? 

Send us your views on this blog and become part of the ever expanding Musculoskeletal Elf community. Post your comment below, or get in touch via social media (FacebookTwitterLinkedInGoogle+).


  • Effect of Therapeutic Aquatic Exercise on Symptoms and Function Associated With Lower Limb Osteoarthritis: Systematic Review With Meta-Analysis. Waller B. Phys Ther. 2014 Oct;94(10):1383-95 [Abstract]
  • OMERACT Outcome Measures in Rheumatology
  • COMET INITIATIVE Core Outcome Measures in Effectiveness Trials
  • American College of Rheumatology  OA guidelines
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Tracey Howe

Hi I am Tracey Howe. I am a Professor of Rehabilitation Sciences at Glasgow Caledonian University, UK and Deputy Chair of Glasgow City of Science. I am also an editor for the Cochrane Musculoskeletal Review Group and a convenor for the Cochrane Health Care of Older People Field. I am a Trustee of the Picker Institute Europe. I started my career as a physiotherapist in the National Health Service in England. I have extensive experience of assessing the quality of research in Universities in the UK and internationally. I enjoy strategic visioning, creative problem-solving, and creating vibrant, multi-disciplinary environments, through collaboration, partnerships, and relationships, that empower others to succeed.

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