As orthopaedic and rehabilitation professionals, we frequently encounter patients recovering from Total Knee Arthroplasty (TKA). A recurring debate in orthopaedic surgery—which directly impacts our postoperative rehabilitation strategies—is the choice between Cruciate Retaining (CR) and Posterior Stabilized (PS) implant designs. While both systems are highly prevalent in modern orthopaedic practice, controversies persist regarding their respective functional outcomes, range of motion capabilities, and overall survivorship. A recent prospective, randomized controlled trial sheds crucial light on these factors, providing valuable insights for physiotherapists guiding patients through their recovery journeys.
Methodological Approach to Evaluating TKA Implant Designs
To rigorously assess the differences between these two common implant systems, researchers conducted a prospective, randomized study involving 140 patients diagnosed with severe knee osteoarthritis. Each participant was scheduled for an unconstrained TKA and was randomly assigned to receive either a CR or a PS implant. The research team meticulously tracked the patients’ progress by evaluating their Range of Motion (ROM) and various Patient-Reported Outcome Measures (PROMs). These measures included the Oxford Knee Score, Knee Society Score, European Quality of Life 5 Dimensions 3 Level, University of California Los Angeles Activity scale, and subjective patient satisfaction. Assessments were systematically conducted prior to surgery, and subsequently at 3 months, 1 year, and 2 years postoperatively.
Functional Outcomes: Flexion Gains Versus Overall Patient Satisfaction
The 2-year follow-up results revealed several statistically significant differences, primarily concerning joint kinematics and surgical duration. The PS group experienced a slightly longer surgical duration, averaging 81.4 minutes compared to 76.0 minutes for the CR group. More importantly for rehabilitation professionals, the PS cohort demonstrated superior postoperative flexion. The median flexion achieved in the PS group was 120.0 degrees, whereas the CR group achieved a median of 115.0 degrees. Consequently, the overall range of motion was significantly better in patients who received the posterior-stabilized implant.
Despite these measurable kinematic advantages in the posterior-stabilized group, the PROMs painted a different picture regarding subjective recovery. Patient satisfaction, perceived quality of life, and functional scoring did not significantly differ between the two cohorts. From a survivorship standpoint, both implants performed exceptionally well, with zero revisions reported in either group at the two-year mark. Complication rates remained low across the board, though three patients required manipulation under anesthesia (two in the CR group and one in the PS group) to address stiffness.
Clinical Implications for Orthopaedic Rehabilitation Professionals
For physiotherapists and orthopaedic specialists, these findings underscore a vital clinical nuance: while posterior-stabilized implants may facilitate a statistically better flexion capability, this biomechanical advantage does not automatically translate to higher subjective patient satisfaction or superior perceived functional capacity. The cruciate-retaining implant design remains a highly reliable and effective option for patients presenting with an intact posterior cruciate ligament. When setting rehabilitation goals, therapists should recognize that a 5-degree difference in terminal flexion—while statistically significant—may not clinically alter the patient’s daily functional independence or overall happiness with their joint replacement. Tailoring our rehabilitation protocols to the individual’s specific functional needs, rather than focusing solely on maximizing numerical flexion values, remains the gold standard in postoperative TKA care.
References
Tille, E., Beyer, F., Lützner, C., Postler, A., & Lützner, J. (2024). Better Flexion but Unaffected Satisfaction After Treatment With Posterior Stabilized Versus Cruciate Retaining Total Knee Arthroplasty – 2-year Results of a Prospective, Randomized Trial. The Journal of Arthroplasty. https://pubmed.ncbi.nlm.nih.gov/37598783/
