Impaired Foot Plantar Flexor Muscle Performance in Individuals With Plantar Heel Pain and Association With Foot Orthosis Use.

Study Design Controlled laboratory study. Background Plantar heel pain is one of the most common foot and ankle conditions seen in clinical practice, and many individuals continue to have persisting or recurrent pain after treatment. Impaired foot plantar flexor muscle performance is a factor that may contribute to limited treatment success, but reliable methods to identify impairments in individuals with plantar heel pain are needed. In addition, foot orthoses are commonly used to treat this condition, but the implications of orthosis use on muscle performance have not been assessed. Objectives To assess ankle plantar flexor and toe flexor muscle performance in individuals with plantar heel pain using clinically feasible measures and to examine the relationship between muscle performance and duration of foot orthosis use. Methods The rocker-board plantar flexion test (RBPFT) and modified paper grip test for the great toe (mPGTGT) and lesser toes (mPGTLT) were used to assess foot plantar flexor muscle performance in 27 individuals with plantar heel pain and compared to 27 individuals without foot pain who were matched according to age, sex, and body mass. Pain ratings were obtained before and during testing, and self-reported duration of foot orthosis use was recorded. Results Compared to the control group, individuals with plantar heel pain demonstrated lower performance on the RBPFT (P = .001), the mPGTGT (P = .022), and the mPGTLT (P = .037). Longer duration of foot orthosis use was moderately correlated to lower performance on the RBPFT (r = -0.52, P = .02), the mPGTGT (r = -0.54, P = .01), and the mPGTLT (r = -0.43, P = .03). Conclusion Ankle plantar flexor and toe flexor muscle performance was impaired in individuals with plantar heel pain and associated with longer duration of self-reported foot orthosis use. J Orthop Sports Phys Ther 2016;46(8):681-688. Epub 3 Jul 2016. doi:10.2519/jospt.2016.6482.