Purpose: Posterior capsular contracture is a potential consequence of osteoarthritis, post-traumatic arthritis, and surgical procedures of the knee. Many patients who undergo TKA will be found to have some degree of flexion contracture intraoperatively, which necessitates posterior capsular release. There is no information in the literature about the safety of posterior capsular release done during TKA. The present cadaveric study investigates the safety of posterior capsular release during TKA. Methods: This study involved ten fresh-frozen cadaver specimens, each of which underwent three successive releases of the posterior capsule medially, laterally, and in the midline. One senior joint surgeon performed this procedure with a 1.27 cm curved osteotome, hugging the bone posteriorly on the distal aspect of the femur until the osteotome moved freely behind the bone without resistance. The distance from the distal aspect of the femur to the tip of the osteotome was then measured. Finally, the popliteal fossa was dissected, and the course of the neurovascular bundle was followed to assess for any macroscopic injury. Results: The capsule was penetrated at a median depth of 13.6 cm (range 10.3–17.6). Even at this depth, no injuries to the popliteal artery, tibial nerve, or popliteal vein occurred in any of the 30 penetrating events. Conclusion: This study suggests that posterior capsular release can be performed safely with this technique.