Shattering the 4mm Myth: What Really Happens When We Cut the PCL

New in vivo data prove the historical 4mm flexion gap rule is vastly overstated.

For decades, it has been accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion space by approximately 4mm. Because of this, surgeons were taught that sacrificing the PCL required elevating the joint line to avoid flexion instability.

Unfortunately, this doctrine is based on historical studies of limited size with variable technique. In many cases, these foundational studies were performed in cadaveric specimens where dynamic stabilizers were deficient, or in small cohorts heavily weighted to the female gender.