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  • Study: Optimal Exercise Dose for Knee Disorders Still Unclear

    While much research has shown positive effects of therapeutic exercise for common knee disorders, “optimal dosing is still unclear,” say experts, largely a result of the way authors report their results. Identifying the best dosage is important, they write, because overdosing can have adverse effects, while underdosing can lead to no improvement for the patient.

    In a systematic review published in the Journal of Orthopaedic and Sports Physical Therapy (abstract only available for free), authors examined 45 “fair-quality” studies on the use of therapeutic exercise to treat knee osteoarthritis (OA), patellar tendinopathy, or patellofemoral pain (PFP). Researchers analyzed duration of a single session, frequency of sessions, total number of sessions, duration of treatment, and effect size. Here's what they found:

    • Effect sizes in the included studies varied widely because so many different outcome measures were used, even for the same conditions.
    • For all 3 conditions, some studies did not report or were unclear about the length of each therapy session, frequency of sessions, and whether or not the exercise was supervised.
    • While nearly all studies clearly reported total number of sessions, the number ranged from 3 to 108 for knee OA, from 36 to 180 for patellar tendinopathy, and from 12 to 146 for PFP.
    • Researchers were able to identify only 3 trends from their analysis—all for knee OA. Both 24 total number of sessions and 8-week and 12-week durations were most often related to large effect sizes.
    • Once-per-week session frequency had no effect for knee OA.

    The review’s findings illustrate the challenge of appropriate dosing.

    “Exercise dosing is complex,” note authors, speculating that “an identical bolus of 315 minutes of exercise per week could be disseminated in a variety of ways.” More frequent sessions could be more effective, they write, but that would likely be affected by the duration and intensity of each session.

    Authors acknowledge the balancing act between tailoring exercise prescription to each patient while establishing general dosage parameters that help “standardize effective care, inform clinical practice guidelines, and decrease dosage variance in clinical trials.” It is critical, they say, to improve the quality of dosage reporting in clinical trials, because “these data can better allow researchers to fine tune exercise dosage in subsequent trials, and improve our understanding of exercise parameters that work better than others.”

    Research-related stories featured in PT in Motion News are intended to highlight a topic of interest only and do not constitute an endorsement by APTA. For synthesized research and evidence-based practice information, visit the association's PTNow website.

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