Equids can be distinguished from every other extant mammal by their monodactyl feet. Classically, equid evolution is portrayed as a linear, gradual evolution from tetradactyly to monodactyly, culminating in the modern monodactyl genus Equus (including the domestic horse). Although the linearity of this locomotor transition has now been reassessed in favour of a more complex evolutionary history, the musculoskeletal and physiological similarity of modern equid limbs remains unexplored. Are domestic horse limbs representative for wild equids (e.g., zebras, onagers, etc.), or are there substantial differences in their muscle architecture or myological arrangement which might affect efforts to biomechanically model the musculoskeletal system of extinct species? Here, we explore this question by quantitatively describing the forelimb muscle architecture of all extant Equus species. Gross dissections were performed to record origin and insertions sites, and quantitative metrics recorded (muscle-tendon unit (MTU) length, MTU mass, muscle mass, pennation angle, and fascicle length). Muscle physiological cross-sectional area (PCSA) and ligament (and tendon) anatomical cross-sectional area (ACSA) were then calculated. Results confirm attachment sites of all muscles are homologous across all species, with little individual variation. When normalised for size, the forelimb muscles of caballines, zebras, and wild asses exhibit comparable muscular architecture and force-generating capacities. Although limited by sample size, these results indicate that scaled data for modern equids (domestic and wild) are very comparable, which will facilitate much smoother translation of experimental data from domestic horses into digital simulation of (at least the later stages of) the equid locomotor transition.