Introduction. Orthopaedic and trauma surgeons not infrequently encounter the hallucal interphalangeal joint sesamoid (HIPJS) in irreducible traumatic dislocations. However, patients with the classic triad of plantar keratoma beneath a hyperextended interphalangeal (IP) joint associated with stiffness of the first metatarsophalangeal joint tend to present to podiatrists rather than orthopaedic surgeons. Methods. We present our experience with the HIPJS following first metatarsophalangeal joint (MTP1) arthrodesis in 18 feet of 16 women, aged 42 to 70 years old. Where CT scan was available, volume of the HIPJS was determined using Vitrea Software. Results. Two groups of patients were identified. Group 1 consisted of 12 feet in 11 women, who developed a painful keratoma beneath a gradually hyperextending IP joint of the great toe, at varying intervals (range 6 to 75 months) following MTP1 arthrodesis. Group 2 comprised 6 feet in 5 women who had undergone MTP1 arthrodesis but reported no symptoms in relation to an undetected and/or recognized, but unexcised HIPJS (range 15 to 97 months). We found no difference in average size of the HIPJS between Groups 1 and 2 (190.42 mm. 3. and 196.47 mm. 3. , respectively). Clinically, all toes had been fused in good position and no difference existed in the post-operative angle subtended by the proximal phalanx of the arthrodesed big toe with the first metatarsal between the 2 groups. A good outcome followed removal of metalwork and excision of the HIPJS in the symptomatic patients. Conclusion. Think of a HIPJS in the patient who presents with a painful plantar keratoma beneath a hyperextended interphalangeal joint following MTP1 arthrodesis. Do not rush into a Moberg osteotomy as this will only push the big toe higher against the toe-box. Consider prophylactic excision of a HIPJS prior to MTP1 arthrodesis