Objectives : In this study, we assessed the muscle contraction pattern of each toe by stimulating the flexor hallucis longus (FHL) and flexor digitorum longus (FDL) muscles in patients with claw foot deformity caused by spasticity in the lower extremity in order to increase the benefit of their botulinum toxin treatments. Subjects and Methods : Fifteen post-stroke patients (11 male and 4 female ; mean age, 62.3 years) were recruited for the study. In this observational study, the muscle contraction patterns of the hallux and digits on electrical stimulation of the FHL or FDL were examined by two doctors, and the data was then analyzed. In addition, the FHL and FDL were identified in 6 feet from 3 cadaver specimens below the ankle to near the end of each muscle on each toe. Results : In muscles that could be observed, muscle contraction was observed in the hallux in every subject and in the second digit in 92.3% subjects when the FHL was stimulated electrically. Muscle contraction was not observed in the second digit in 64.3% of the subjects when the FDL was stimulated electrically. In the cadaver dissections, the tendons of the FHL sent fibers to the FDL tendons in all 6 feet examined. Conclusion : In conclusion, when botulinum toxin is to be injected into the FHL or FDL muscle for treating claw foot deformity in patients with lower extremity spasticity, especially when the treatment target is the second digit, the injection should be performed not only in the FDL muscle, but also in the FHL muscle to increase the effectiveness of the treatment.