Core muscle recruitment pattern during voluntary heel raises is different between patients with patellofemoral pain and healthy individuals

- GM and TrA/IO activated before the prime mover's contraction in control subjects.
- The activation of the prime mover preceded the response of ES in both groups.
- PFP subjects showed delayed contraction of TrA/IO compared with control subjects.
- The recruitment order of the core muscles differed between the groups.

BackgroundRecent studies suggest that the inconsistent outcomes of patellofemoral pain (PFP) treatment may result from the unclear understanding of changes in the structures remote from the knee joint. Due to the crucial influence of core stability on the knee function, this study aimed to evaluate the recruitment pattern of core muscles in individuals with and without PFP.MethodsSixty women aged 18 to 40 years, including 30 subjects diagnosed with PFP and 30 healthy controls rose on to their toes as quickly and strongly as possible in response to a sound alarm in standing position. Electromyographic onsets of the transversus abdominis (TrA)/internal oblique (IO), erector spinae (ES), and gluteus medius (GM) muscles were expressed relative to the electromyographic onset of the prime mover (i.e. soleus). Independent t-tests were performed to compare the onsets of each muscle between the groups. The nonparametric Friedman test and the post-hoc of Wilcoxon signed-rank test were used to describe the muscle activation pattern within the groups.ResultsThe results revealed different recruitment patterns of the core muscles between the groups. In the healthy group the GM and TrA/IO contracted, almost simultaneously, in anticipation of the prime mover contraction (sol). However, in PFP subjects a significant delay in the contraction of TrA/IO changed the pattern of muscle activation.ConclusionThe findings demonstrate that muscular stabilization of spine is altered in the presence of PFP and suggest that treatment techniques aimed at improving core stability could be appropriate in the management of PFP.