Several methods have been described to quantify the first ray mobility. They all have certain disadvantages (great size, sophistication, or lack of validation). The objective of this work was to study the validity and reliability of a new instrument for the measurement of first ray mobility. Anterior-posterior radiographs were obtained from 25 normal feet and 24 hallux valgus feet, with the first ray in a neutral position, maximally dorsiflexed and maximally plantarflexed. The first ray mobility was radiographicaly measured in both groups, and was also manually examined with the new device. A cluster analysis determined whether normal and hallux valgus feet were correctly classified, and a graphic analysis of Bland-Altman was performed to compare the radiographic and manual measurement techniques. Based on the radiographs, the first ray mobility only showed significant differences in dorsiflexion between both groups (P = 0.015). First ray dorsiflexion, plantarflexion and total range of motion measured with the new device were different between both groups (P = 0.040, P = 0.011 and P = 0.006, respectively). The silhouette measure of the cohesion and separation coefficients from the cluster analysis was greater than 0.50 for the dorsiflexion, plantarflexion and total range of motion obtained from the radiographs and from the new device. The Bland-Altman graph suggested that 96% of the data presented agreement between both measurement methods. These results suggested that the new instrument was valid and reliable.

The aim of this study was to analyze the joint characteristics of the foot and ankle in competitive swimmers aged 16–18 and 19–24 years and their relationship with the presence of muscle pain during swimming. A total of 74 swimmers were evaluated: 38 ‘junior’ (16–18 years) and 36 ‘senior’ (19–24 years). The following parameters were recorded: ankle dorsiflexion, rearfoot mobility, first metatarsophalangeal dorsiflexion, presence of hallux valgus, foot posture, first ray mobility, arch height, and plantar pressure. Additionally, the frequency and location of muscle pain in the triceps surae were analyzed. A cluster analysis was performed to identify variables that differentiated both groups. Ankle dorsiflexion was limited in both groups, with a greater restriction observed in adults (p < 0.001 with an extended knee; p < 0.014 with a flexed knee). The predominant foot type was the cavus foot. The most common pain was localized in the triceps surae, followed by the plantar musculature, with no significant differences between groups. Swimmers exhibited gastrocnemius shortening, which could limit ankle dorsiflexion and contribute to the onset of muscle pain in the leg and foot. These findings suggest the importance of incorporating lower limb flexibility strategies into the training of competitive swimmers.

The first ray plays a fundamental role in foot biomechanics, particularly in stabilizing the medial longitudinal arch and enabling efficient weight transfer during the mid-stance and propulsion phases of gait. When dorsiflexed—a condition known as metatarsus primus elevatus—especially in its flexible form, this structure disrupts load distribution, impairs propulsion, and contributes to various clinical symptoms. Despite its clinical importance, the biomechanical impact of orthotic elements placed beneath the first ray remains underexplored. This study aimed to quantify the variations in medio-lateral (Fx), antero-posterior (Fy), and vertical (Fz) force vectors generated during gait in response to different orthotic elements positioned under the first ray. A quasi-experimental, post-test design was conducted involving 22 participants (10 men and 12 women) diagnosed with flexible metatarsus primus elevatus. Each participant was evaluated using custom-made insoles incorporating various orthotic elements, while gait data were collected using a dynamometric platform during the mid-stance and propulsion phases. Significant gait-phase-dependent force alterations were observed. A cut-out (E) reduced medio-lateral forces during propulsion (p < 0.05), while a kinetic wedge (F) was correlated with late-stance stability (r = −0.526). The foot posture index (FPI)/body mass index (BMI) mediated the vertical forces. The effect sizes reached 0.45–0.42 for antero-posterior force modulation. Phase-targeted orthoses (a cut-out for propulsion, a kinetic wedge for late stance) and patient factors (FPI/BMI) appear to promote biomechanical efficacy in metatarsus primus elevatus, enabling personalized therapeutic strategies.