Arthroscopic Arthrolysis of a Completely Ankylosed Knee in Extension via a Superolateral Portal-First Approach.

Complete knee ankylosis in full extension following fracture surgery poses a distinct technical challenge for arthroscopic intervention, because standard portal placement requires at least partial knee flexion to open the tibiofemoral joint space. We report a 61-year-old woman who developed complete left knee ankylosis at 0° three months after open reduction and internal fixation with bone grafting of the proximal tibia at an outside institution. Physical examination revealed a completely rigid knee with no passive or active flexion and severely restricted patellar mobility, and conservative management including physical therapy had failed. We employed a superolateral portal-first approach with the knee in full extension, targeting the preserved suprapatellar potential space beneath the superior patellar pole. Through systematic proximal-to-distal arthroscopic debridement of dense intra-articular adhesions involving the suprapatellar pouch, peripatellar gutters, infrapatellar region, and intercondylar notch, followed by gentle incremental manipulation, intraoperative flexion of 90° was achieved. At discharge on postoperative day 8, the patient had active flexion of 50°, passive flexion of 85° on continuous passive motion, and full extension. At one-month follow-up, she maintained full active extension with no extensor lag and had achieved active flexion of 90° by goniometry, and no complications occurred. No validated patient-reported outcome measure was recorded. The suprapatellar space typically retains a residual potential space even in severely ankylosed joints and therefore provides a reliable initial arthroscopic entry point; this proximal-to-distal strategy with progressive portal creation enables access without the need for initial knee flexion. A superolateral portal-first technique may represent a useful option for obtaining initial arthroscopic access in selected cases of complete post-traumatic knee ankylosis. A single case observed for one month cannot establish clinical success or durability, and no claim of superiority over conventional anterior portal techniques is made.