Pain, balance and mobility in people one year after total knee arthroplasty: A pilot cross-sectional study contrasting posterior-stabilized and medial-pivot designs

Background Total knee arthroplasty (TKA) is a common treatment for severe knee osteoarthritis. TKA designs have evolved from posterior-stabilized systems (PS-TKA) developed in the late 70 s that replicate posterior-cruciate ligament function to medial-pivot systems (MP-TKA) developed in the early 90 s that more closely mimic natural knee kinematics. This study aimed to test the hypothesis that people with MP-TKA have better postoperative outcomes than PS-TKA, and their balance control is more akin to age-matched asymptomatic controls.Methods Fifty-seven participants (20 PS-TKA, 18 MP-TKA and 19 asymptomatic controls) were recruited. At 1-year post-TKA, pain, knee stiffness and physical function were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Static balance, mobility and gait stability were assessed using wearable devices during the near tandem stance, timed-up-and-go (TUG) and six-minute walk (6MWT) tests.Results Compared to asymptomatic controls, both TKA groups reported significantly more pain and stiffness, and demonstrated reduced functional mobility, increased stride-time-variability and impaired balance; indicating increased fall risk. After Bonferroni adjustment, no significant differences were observed between PS-TKA and MP-TKA participants. However, there was a trend for increased anteroposterior sway of the lumbar and head regions in the MP-TKA participants when undertaking the near tandem stance test.Conclusions Contrary to the hypothesis, the MP-TKA patients did not have less pain or better balance and mobility performance than the PS-TKA patients 1 year after surgery. Future longitudinal research should determine whether the two types of patients display different pain, balance controls and mobility over the first year postoperative period.