Relationship between lower limb muscle strength and hallux valgus severity in older people

Objective: To examine differences in lower limb muscle strength between older people with varying degrees of hallux valgus deformity. Methods: Muscle strength was measured at the knee, ankle and foot using hand-held dynamometry and a clinical test of toe strength (the paper grip test) in 157 older people (99 women and 58 men) aged 65 to 91 (mean 74.1, SD 5.9) years. Hallux valgus severity was documented as none, mild, moderate or severe using validated photographs. Differences in muscle strength according to hallux valgus severity were evaluated using analysis of variance, adjusting for age. Paper grip test performance was compared across the hallux valgus severity groups using the chi-square (χ2) statistic. Results: Knee extension, ankle joint dorsiflexion, ankle joint plantar flexion, ankle joint inversion, ankle joint eversion and lesser toe plantarflexion strength were not significantly different across the four hallux valgus severity groups. However, there was a significant, dose-response reduction in hallux plantarflexion strength with increasing severity of hallux valgus. This persisted after adjustment for age (F3 = 5.5, p = 0.001) with a medium effect size (partial η2 = 0.10). The number of participants who could successfully complete the paper grip test of the hallux significantly reduced across the four hallux valgus categories (χ2 = 18.5, p < 0.001). Conclusions: There is a specific and progressive reduction in hallux plantarflexion strength with increasing severity of hallux valgus in older people. This finding has potential implications for both the aetiology and treatment of this common and disabling condition.