Misdiagnosis of Calcaneal Chondrosarcoma as Plantar Fasciitis: A Case Report

Chondrosarcoma is the most common malignant bone tumour amongst the elderly. However, they often present as diagnostic dilemmas leading to diagnostic delays, leading to poor prognosis in elderly patients. Chondrosarcoma of the foot is also exceedingly rare, comprising <6% of bone tumors, where its clinical presentation can mimic common soft tissue conditions such as plantar fasciitis. We report the case of a 79-year-old female who presented with non-mechanical right foot pain involving the heel, initially misdiagnosed as plantar fasciitis for two years. Her foot pain remained recalcitrant to conservative management. Advanced imaging performed revealed a large lytic lesion in the calcaneus, initially thought to represent an aneurysmal bone cyst. Confirmatory pre-operative biopsy revealed a calcaneum chondrosarcoma. Below-knee amputation (BKA) was performed, and the outcome was good, with no reported local recurrence or metastases. Bone malignancy should be considered as a key differential in all cases of non-mechanical pain. As it may be challenging to clinically differentiate between recalcitrant plantar fasciitis and other malignant conditions of the foot, imaging should be mandatory for all patients presenting with non-mechanical pain.