Intrinsic foot muscle size and quality in a single leg weight bearing position across foot posture types in individuals with Patellofemoral Pain compared to healthy

Abstract

Objective: To identify if any differences exist in IFM size and quality in single leg weight bearing position between healthy and PFP participants based on foot posture. Design: Cross-sectional, matched case-comparison study Setting: University Laboratory Setting Participants: 35 PFP (age:20.46 ± 3.79yrs, mass:73.28 ± 26.58 kg, height:170.80 ± 11.91 cm) and 35 healthy (age:20.40 ± 3.16yrs, mass:64.76 ± 11.52 kg, height:169.55 ± 9.10 cm) participants Methods: After measuring Foot Posture Index (FPI), ultrasound images (USI) of Abductor Hallucis (AH), Flexor Digitorum Brevis (FDB) and Quadratus Plantae (QP) were taken in a single limb weight bearing position. Cross-sectional area (CSA) and echogenicity were measured on the USI. Results: FPI was not different between groups (PFP:2.34 ± 3.76, Healthy:2.34 ± 3.10, 9 pronated and 26 non-pronated in both groups). AH CSA was smaller in PFP than healthy group (PFP:0.030 ± 0.01 cm (Smith et al., 2018)/kg, Healthy:0.042 ± 0.01 cm (Smith et al., 2018)/kg, P < 0.001) with a large effect (d = −1.20(-1.71, −0.69). There were no other significant group main effects or group-by-FP interactions in AH/FDB/QP CSA or echogenicity. Conclusion: AH CSA was smaller in PFP than healthy controls, but no difference in CSA or echogenicity of FDB/QP exist, as well as no difference in foot posture between groups. While single limb weight bearing, the PFP group presented with a smaller IFM which provides eccentric control of medial longitudinal arch, which may have implications up the chain during weight bearing functional tasks.