Objective: To evaluate the range of motion (ROM) of the knee in patients with severe post-traumatic knee arthrofibrosis after being treated with arthroscopic fibroarthrolysis (AFA) and manipulation under anesthesia (MUA). Methods: Case series of patients with severe post-traumatic knee arthrofibrosis who underwent AFL + MUA in a national referral center. The primary outcome to be assessed was ROM before and after surgery and then at 3-month intervals until a minimum follow-up of one year was completed. Results: 51 patients were included. The main injuries preceding the stiffness were tibial plateau fracture (37.3%), distal femur fracture (27.5%), and femoral shaft fracture (15.7%). Forty-five patients had severe flexion deficits with a median preoperative flexion of 70°. Intraoperative flexion significantly improved to 110°. Significant loss of flexion was observed at 3 and 6 months, however, patients regained ROM in the 9 and 12-month follow-ups. At discharge, 80% of the patients achieved flexion of 90° or more. There were 4 intraoperative complications and 3 reinterventions were performed. Conclusion: AFA + MUA can help patients with severe post-traumatic knee arthrofibrosis to recover ROM in most cases. However, this procedure is not without risks and complications, therefore, careful consideration should be given to its indication and execution.