Intrinsic Foot Muscle Cross‐Sectional Area on MRI in People With and Without Plantar Heel Pain: A Cross‐Sectional Observational Study

Introduction This study compared the cross‐sectional areas (CSA) of key intrinsic foot muscles in people with and without plantar heel pain (PHP). Methods Seventy‐five adults participated in the study: 50 participants with PHP and 25 age‐, sex‐, and body mass index (BMI)‐matched participants without PHP (control group). Cross‐sectional images were generated using 3.0T magnetic resonance imaging (MRI). CSAs of four intrinsic foot muscles—abductor hallucis, quadratus plantae, flexor digitorum brevis and abductor digiti minimi—were measured. The difference in CSA of each muscle was compared between the groups using independent samples t ‐tests and Cohen's d effect sizes were calculated. Results Participants were well matched: mean age 49.1 and 48.9 years, women accounted for 58% and 56%, and BMI 30.6 kg/m 2 and 30.2 kg/m 2 in the PHP and control groups, respectively. There were no significant differences in mean CSAs for all four muscles ( p > 0.05) between the PHP and control groups, and effect sizes were tiny or very small. Conclusion This study found no differences in muscle CSAs of key intrinsic muscles of the foot in people with and without PHP, indicating that people with PHP do not have key intrinsic foot muscle size deficits. As such, intrinsic muscle size does not appear to be a logical therapeutic target for PHP. Clinicians translating our findings into practice should, therefore, consider whether strengthening interventions targeting intrinsic muscles in PHP are warranted.