There has been a resurgence of popularity in performing bicruciate-retaining (BCR) total knee arthroplasty (TKA) as opposed to the more common posterior-stabilized (PS). BCR may be better for young and active patients since it restores knee kinematics better than other prosthetic designs. However, there is a belief in the community that BCR results in stiffer knees. There is not yet any study that shows clear clinical differences between BCR and PS TKAs. This study aims to clarify this point of contention.

A prospective randomized control trial was conducted where patients were randomized to have either BCR or PS TKA implanted using a spacer-based gap balancing technique. A total of 32 BCR and 34 PS knees were evaluated (54 patients). Results were obtained at the preoperative visit and the subsequent postoperative visits up to 2 years and above. In this study, knee range of motion measurements, Knee injury and Osteoarthritis Outcome Score (KOOS), as well as Knee Society (KS) knee and function scores were compared between groups and visits.

There was a significant difference in maximum knee flexion between BCR and PS patients at 6 weeks (BCR_mean 94.8°, PS_mean 113.6°, P<0.001), 6 months (BCR_mean 109.5°, PS_mean 123.2°, P 0.017), and 12 months (BCR_mean 113.5°, PS_mean 126.1°, P 0.003). No significant difference was found between the two groups at 2 years (BCR_mean 120.4°, PS_mean 128.0°, P 0.087). Similar results were found when the knees with a preoperative maximum flexion≥130° were analyzed separately. The KOOS and KS knee and function scores were globally similar at every visit between the groups as neither yielded significant differences, with the exception of the KOOS score at 6 weeks that was higher for PS knees.

The results confirm the suspicion that BCR TKA results in stiffer knees than PS TKA during the early postoperative period. However the difference in maximum flexion decreased and tended to resolve by the 2-year postoperative visit. The difference also did not seem to have an impact on the various clinical and functional outcome measurements that were collected after 6weeks.

BCR TKA does not result in stiffer knees than PS TKA after 2years. There appears to be a stiffening phenomenon that occurs after BCR TKA compared to PS TKA but it seems to resolve over time. Further investigation on the causes of this phenomenon is warranted. Further follow-up of this patient cohort will provide additional relevant information.