Individuals with patellofemoral pain syndrome have altered inter-leg force coordination.
BACKGROUND
Patellofemoral pain syndrome (PFPS) is one of the most common musculoskeletal disorders. Pain may be further exacerbated by atypical motor coordination strategies. It has been thought that low coordination variability may concentrate loads onto painful knee tissues.


RESEARCH QUESTION
To investigate if inter-limb force coordination is altered between individuals with and without PFPS.


METHODS
31 individuals (control = 17, PFPS = 14) performed bilateral vertical hopping, on two force plates at three frequencies (2.2, 2.6, 3.0 Hz). Uncontrolled manifold analysis (UCM) was used to provide an index of motor abundance (IMA) in the coordination of inter-limb forces to stabilize the two-limb's total force. UCM was applied to the study of forces in each plane (medial-lateral (ML), anterior-posterior (AP), vertical). Bayesian Functional Data Analysis was used for statistical inference. We calculated the mean (u) with 95 % credible interval (CrI) of the difference ΔIMAcon>PFPS between the two groups. We also calculated the probability PΔIMAcon>PFPS>0data).


RESULTS
Individuals with PFPS had the greatest significant decrement from controls at 6% of stance hopping at 2.6 Hz by a mean difference of -0.23 for ML GRF; at 19 % of stance hopping at 2.2 Hz by a mean difference of -0.14 for AP GRF; and 52 % of stance hopping at 2.6 Hz by a mean difference of -0.14 for vertical GRF. For vertical GRF, there was a > 0.95 probability that controls had greater IMA than individuals with PFPS hopping between 12-13% of stance at 2.2 Hz, and between 48-55% at 2.6 Hz.


SIGNIFICANCE
Individuals with PFPS have reduced inter-leg force coordination for impact force attenuation and body support, compared to asymptomatic controls. The present study provides insights into a plausible mechanism underpinning persistent knee pain which could be used in the development of novel rehabilitative approaches for individuals with PFPS.
['Liew|Bernard X W|BXW|', 'Abichandani|Deepa|D|', 'De Nunzio|Alessandro Marco|AM|']
D000293:Adolescent D000328:Adult D001499:Bayes Theorem D001696:Biomechanical Phenomena D016022:Case-Control Studies D005260:Female D006801:Humans D007866:Leg D008297:Male D008875:Middle Aged D009068:Movement D046788:Patellofemoral Pain Syndrome D055815:Young Adult
Patellofemoral pain syndrome Coordination Uncontrolled manifold Biomechanics Motor control Spring-mass