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Purpose There is a lack of robust evidence for the magnitude of the efects of posterior capsular release (PCR) on intraoperative component gaps during total knee arthroplasty (TKA). The purpose of the present study was to quantify and compare the efects of partial versus full PCR on the intraoperative component gaps at various degrees of lexion during posteriorstabilized TKA. Methods Full PCR was performed on 39 consecutive cases (full PCR group), and partial PCR (the medial side up to and including the intercondylar notch) was performed on the subsequent 39 consecutive cases (partial PCR group) during posterior-stabilized TKA using the measured resection technique for varus knee osteoarthritis. Medial component gaps and varus angles at 0°, 10°, 45°, 90°, and a maximum of lexion were measured with a tensor device before and after the PCR. Diferences between the two groups in post-release medial component gap increase and post-release joint varus angle increase were assessed using a t test. Pre-to post-release medial component gaps and joint varus angles in each group were compared using a paired samples t test. ResultsIn both groups at 0° and 10° of lexion, post-release medial compartment gaps were signiicantly greater than prerelease gaps (all P < 0.001). At 45°, 90° and maximum lexion, the medial compartment gap increase did not exceed the minimal detectable change in either group. At 0° and 10° of lexion, there was no signiicant diference in post-release medial compartment gap change between the two groups. In the full PCR group, post-release joint varus angles at 0° of lexion were signiicantly greater than pre-release angles (P < 0.001), while there was no signiicant pre-and post-release diference in the partial PCR group. The change in post-release joint varus angles at 0° of lexion was signiicantly greater in the full PCR group than in the partial PCR group. Conclusion Both full and partial PCR show similar clinical usefulness for increasing the medial component gap at extension and reducing component gap mismatch. A partial PCR can be used to avoid increasing joint varus angles at 0° of lexion. Level of evidence Level 2 (prospective comparative study).