Temporomandibular joint (TMJ) ankylosis is a serious disabling condition characterized by fusion of the mandibular condyle with the glenoid fossa, disc, and/or eminence, resulting in severely restricted mouth opening and significantly reduced mandibular movements. The condition often has a deteriorating effect on the patient's daily functions such as speech, chewing, breathing, and oral hygiene as well as their wellbeing and quality of life. Furthermore, childhood TMJ ankylosis frequently has a detrimental impact on the facial growth resulting in facial asymmetry, micrognathia, and/or class II malocclusion with posterior or anterior open bite. Trauma is the main cause of TMJ ankylosis, but the condition can also occur as a result of surgery, local or systemic infections, or systemic disease. Surgery is the mainstay of treatment, and several approaches have been applied, including gap arthroplasty (GA), interpositional gap arthroplasty (IGA), reconstruction arthroplasty (RA), or distraction osteogenesis (DO). The aim of this poster is to present a post-traumatic TMJ ankylosis case in a 12-year-old female patient who reported to our department with a chief complaint of difficulty in opening of the mouth. The maximum mouth opening was limited to 1mm. Interposition gap arthroplasty with temporalis myofascial flap was done followed by aggressive physiotherapy. A good functional and aesthetic result was achieved without further surgery. The results conclude that the following suggested best practice protocol is effective in treating unilateral TMJ ankylosis.