Adhesion of the flexor hallucis longus (FHL) muscle to the distal tibia can occur after distal tibial fracture, distal fibular fracture, low tibial osteotomy, soft-tissue injury at the posterior ankle, subclinical compartment syndrome of the distal deep posterior compartment of the leg, or Volkmann contracture after deep posterior compartment syndrome of the leg. The purpose of this Technical Note is to report the endoscopic approach of FHL muscle adhesiolysis. It is indicated in patients with symptomatic adhesion of the FHL muscle and contraindicated if there is entrapment of the FHL muscle or tendon in the fracture callus or if there is extensive fibrosis and contracture of the FHL muscle as a result of Volkmann contracture after deep posterior compartment syndrome of the leg.