Objective:​ To explore the influence of the joint capsule exerts on the motion of the first metatarsophalangeal joint. To provide information for the clinical treatment of hallux valgus and other operations involving the first metatarsophalangeal joint capsule.

Methods:​ 6 fresh cadaveric foot specimens were used in the experiment. A digital detective device was adopted to measure the motion range of the first metatarsophalangeal joint before and after the medial joint capsule was tightened by the suture. During the measuring process, the distal end of the hallux was loaded to dorsiflexion and plantar flexion with the whole specimen fixed to homemade braces,

Results:​ The dorsiflexion range of the first metatarsophalangeal joint was 68.34°±3.05° and 54.47°±3.95° before and after the tightening of medial joint capsule. The mean plantar flexion range was 33.10°±3.92°and reduced to 24.11°±2.80° with the medial joint capsule tightened. The motion range of dorsiflexion decreased by 13.87°±2.01°, the plantar flexion range decreased by 8.99°±2.57°, and the total motion range in the sagittal plane decreased by 22.86°±2.61° after the medial joint capsule was tightened. Paired t-test showed the difference was statistically significant (P < 0.05).

Conclusions:​ Surgical correction of hallux valgus deformity should take the joint capsule into consideration. Reparation of the capsule should be appropriate to avoid over tightening. Earlier movement of the first metatarsophalangeal joint after the operation should be suggested in order to resume the normal motion range.