Hidden Adaptations: Ultrasound Evidence of Intrinsic Foot and Tendon Changes in Basketball Players with Hallux...

Background: Hallux limitus (HL) is a restriction of first metatarsophalangeal joint dorsiflexion, commonly linked to foot biomechanics-related disorders or trauma, increasing sports injury risk. It involves plantar fascia tension, compensations, and tendon adaptations. Rehabilitative ultrasound imaging (RUSI) accurately assesses musculoskeletal changes, supporting physiotherapy evaluation and the study of HL-related structural adaptations. Objectives: Comparing the thickness and cross-sectional area (CSA) of flexor hallucis brevis (FHB), flexor digitorum brevis (FDB), abductor hallucis (AbH), and quadratus plantae (QP) muscles, as well as the thickness of the plantar fascia (PF), Achilles tendon (AT), and plantar calcaneal fat pad (CFP), between participants with and without HL. Methods: Case-control study included 80 basketball players recruited from semi-professional teams by consecutive non-probabilistic sampling. Participants were divided into two groups: an HL group (n = 40) and a healthy group (n = 40). Musculotendinous parameters were assessed using RUSI. Results: The FDB, FHB, AB, and QP showed significant reductions in thickness and CSA at rest and at contraction in the HL group. PF thickness increased in participants with HL, while CFP thickness decreased significantly. Significance was established at (p < 0.05). Conclusions: HL participants exhibited reduced muscle size and CSA, increased PF, and lower CFP thicknesses, indicating adaptive tissue alterations.