Roughly 10-15% of TKA patients remain dissatisfied after surgery, partly attributed to non-physiologic knee kinematics. This RCT compared medial pivot TKA (single-radius femur, asymmetric conforming insert) to a conventional posterior-stabilized design in 80 patients at 2-year follow-up. The study asked whether design differences translate into measurable differences in patient performance, reported outcomes, and function.
The trade-off between flexion and functional performance is the central teaching point here.
PS TKA reliably gained ~9° of flexion by 2 years; medial pivot patients actually lost ~6° from their (already adequate) baseline. If your patient's primary goal is deep flexion — for kneeling, prayer position, or high-demand activities — PS has a measurable kinematic advantage from its cam-and-post rollback mechanism.
Flip that around: if the patient's priority is rising from a chair or walking efficiently, medial pivot TKA produced statistically and likely clinically meaningful gains in both timed up-and-go and self-paced walk speed. The authors attribute this to the single-radius femoral design and medial conformity better engaging quadriceps mechanics during functional tasks.
The equivalence in satisfaction scores is clinically important. Despite real, measurable differences in flexion and functional performance tests, patients in both groups were equally satisfied and equally unaware of their implant (Forgotten Joint Score). This suggests that neither design is definitively superior for patient experience, and implant selection may reasonably be guided by the individual patient's functional priorities.
This evidence remains debated — other RCTs have favored PS designs or found no difference — and 2-year follow-up is too short to assess survivorship or long-term wear differences between these bearing geometries.
Roughly 10-15% of TKA patients remain dissatisfied after surgery, partly attributed to non-physiologic knee kinematics. This RCT compared medial pivot TKA (single-radius femur, asymmetric conforming insert) to a conventional posterior-stabilized design in 80 patients at 2-year follow-up. The study asked whether design differences translate into measurable differences in patient performance, reported outcomes, and function.
The trade-off between flexion and functional performance is the central teaching point here.
PS TKA reliably gained ~9° of flexion by 2 years; medial pivot patients actually lost ~6° from their (already adequate) baseline. If your patient's primary goal is deep flexion — for kneeling, prayer position, or high-demand activities — PS has a measurable kinematic advantage from its cam-and-post rollback mechanism.
Flip that around: if the patient's priority is rising from a chair or walking efficiently, medial pivot TKA produced statistically and likely clinically meaningful gains in both timed up-and-go and self-paced walk speed. The authors attribute this to the single-radius femoral design and medial conformity better engaging quadriceps mechanics during functional tasks.
The equivalence in satisfaction scores is clinically important. Despite real, measurable differences in flexion and functional performance tests, patients in both groups were equally satisfied and equally unaware of their implant (Forgotten Joint Score). This suggests that neither design is definitively superior for patient experience, and implant selection may reasonably be guided by the individual patient's functional priorities.
This evidence remains debated — other RCTs have favored PS designs or found no difference — and 2-year follow-up is too short to assess survivorship or long-term wear differences between these bearing geometries.