Background/Purpose:   Osteoarthritis (OA), the most common form of arthritis, is a major cause of pain and disability.  Biomechanical interventions that reduce dynamic loading are a promising strategy to improve pain and retard disease progression, though prior studies in OA have not shown dramatic efficacy.  In addition, the large placebo effect inherent in studies of OA pain make it difficult to prove clinical efficacy in short studies. Here, we present data from a double-blind randomized controlled study of a flexible shoe (“mobility” shoe), which has previously been shown to reduce medial compartment knee loading, on self-reported clinical outcomes over 48 weeks.  

Methods:   Participants were enrolled in a 6-month randomized controlled study of a flexible soled shoe (mobility shoe) vs identical appearing control shoe with stiffer sole.  Participants had the opportunity to continue the study for an additional 18 months.  Here, we evaluate the interim 48 week data.  All participants had radiographic (KL grades ≥ 2) and symptomatic (at least 30/100 mm pain on VAS) medial compartment knee OA.  Investigators and participants were blinded to shoe assignment. Baseline and follow up clinical symptoms were evaluated using WOMAC visual analog scales and modified KOOS questionnaires.  Data were evaluated to determine “responders” according to modified OMERACT-OARSI responder criteria, with Chi-squared analysis to evaluate the difference in number of responders.  Independent samples t-test was used to evaluate differences in percent improvement in WOMAC and KOOS subscales between the groups.

Results: 50 participants were enrolled in the randomized controlled trial, 22 to the active “mobility” shoe and 28 to the control group.  24 participants continued with the study extension, 11 in the “mobility” group (7 female, mean age 59±4 years) and 13 in the control group (10 female, mean age 52±9 years).   Changes in pain and symptoms over 48 weeks are detailed in the Table.  Overall, there were greater improvements in pain, function and quality of life measures in the active mobility group vs control group.  Changes in pain were not correlated with age.  In addition, using OMERACT-OARSI response criteria, the mobility group had significantly more responders (10 out of 11) than the control group (6 out of 13), (Chi squared= 5.37, df=1, p=0.023). Thus, participants who wore the flexible shoe were 1.98 times more likely to show clinical improvement than those in the control.

Conclusion:   These data demonstrate significant clinical improvements in the active group, assigned to flexible footwear, compared to a non-flexible footwear control group, including a higher percentage of OMERACT-OARSI responders and greater percent improvements in self-reported clinical outcomes measures in the active group.  Notwithstanding the small numbers, these results suggest optimism for the long term efficacy of biomechanical interventions for knee OA. 

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