Though form-function relationships of the mammalian locomotor system have been investigated for over a century, recent models of trait evolution have hitherto been seldom used to identify likely evolutionary processes underlying the locomotor system’s morphological diversity. Using mustelid mammals, an ecologically diverse lineage within Carnivora, I investigated whether variation in hindlimb skeletal morphology functionally coincides with climbing, digging, swimming, and generalized locomotor habits by using 15 linear traits collected from 44 species. The sampled traits are composed of the lengths, diameters, and muscle in-lever lengths of the femur, tibia, fibula, calcaneum, and metatarsal III, with these traits being used in a principal components analysis. After mitigating the influence of size, I then subsequently fit competing models of Brownian motion and adaptive trait diversification individually to each of the 15 traits. Mustelids specialized for climbing occupy a region of phenotypic space characterized by a gracile limb skeleton, whereas those specialized for digging and swimming occupy regions characterized by a robust limb skeleton though of differing limb proportions. A model of adaptive evolution is the most likely fit for individual traits of the hindlimb; however, simulating data under models of best fit and fitting the simulated data to the different diversification models reveals low statistical power to rank the models. Though the differences in hindlimb skeletal morphology appears to coincide with locomotor habits, further study, with sampling expanded beyond Mustelidae and including fossil taxa, is necessary to better understand to what degree adaptive evolution shapes the morphological diversification of the locomotor system in mustelids and other mammals.