According to a new study from New Zealand, a couple of things are clear: (1) exercise therapy for individuals with knee osteoarthritis (OA) tends to be more effective when some sessions are spread out over a year as "booster" sessions rather than held every few days over a shorter timeframe; and (2) manual therapy conducted in addition to exercise therapy increases overall treatment effectiveness—but only when it's part of sessions that are conducted in the compressed schedule. In fact, manual therapy actually seemed to decrease effectiveness when it was used in the booster program.
Weird, right? The authors of the study thought so, too. But they have some caveats about that particular result, which they describe as "perplexing."
The study, e-published ahead of print in the Journal of Orthopaedic and Sports Physical Therapy (abstract only available for free), aimed to assess whether exercise therapy for knee OA was more effective when 12 45-minute exercise therapy sessions were provided over 9 weeks, or through a "booster" schedule that provided 8 consecutive sessions during the first 9 weeks, 2 booster sessions at 5 months, 1 booster session at 8 months, and a final booster session at 11 months. A second goal was to find out if the additional manual therapy improved outcomes. Reassessments took place 1 year after treatment began.
Researchers primarily relied on changes in Western Ontario and McMasters Universities Osteorarthritis (WOMAC) scores as the outcome measure for 66 participants with knee OA who were divided into 4 groups: a 9-week exercise therapy group (Ex), a 9-week Ex group that also received manual therapy (Ex+MT), a booster exercise therapy schedule group (ExB), and an ExB group that also received manual therapy (ExB+MT). Overall treatment success was also evaluated according to the Outcome Measures in Rheumatoid Arthritis Research Society International (OMERACT-OARSI) definitions, which rely on a combination of WOMAC scores, pain reduction ratings, functional improvements, and global rating of change.
At the 1-year mark researchers found that when it came to exercise therapy alone, individuals who participated in the booster program averaged scores on the 0-240 WOMAC scale that were 46 points lower than the average for individuals in the 9-week program (lower numbers are preferable). The effectiveness of the 9-week program improved when manual therapy was added, with the Ex+MT group averaging WOMAC scores 37.5 points below the Ex group.
But strangely enough, the addition of manual therapy to the booster group resulted in WOMAC scores that were, on average, almost the same as the scores registered by the group that received only exercise therapy in the 9-week timeframe—a result that seemed to show that adding manual therapy to a booster regimen actually decreased WOMAC scores for this group.
"The finding of an adverse interaction effect between manual therapy and booster sessions … was perplexing," authors write. Though they describe it as "conjecture," they speculate that "the simplest and therefore most likely explanation" is that small group sizes—18 or 19 participants per group—may have introduced instability to the study, which was intended to test main effects for the larger groups (Ex vs ExB, and manual therapy vs no manual therapy).
Authors acknowledge that although the study's findings are strong, the results do not concur with a similar study that found lower-than-expected treatment effects in the Ex group and contradictory interaction effects in the ExB+MT group. These variations underscore the need for more research on the incremental effectiveness of the various approaches, they write.
Authors of the study include J. Haxby Abbott, DPT, PhD, FNZP, G. Kelley Fitzgerald, PT, PhD, FAPTA, Julie Fritz, PT, PhD, FAPTA, and John Childs, PT, PhD, MBA, FAPTA, OCS.