Despite continuing advances, nearly 20% of patients remain dissatisfied with their total knee arthroplasty (TKA) outcomes. Single-radius (SR) and multiradius (MR) TKA designs are two commonly used knee replacement designs based on competing theories of the flexion/extension axis of the knee. Our aim was to characterize stair descent kinematics and kinetics in SR and MR TKA subjects. We hypothesized that 1 year after TKA, patients who received SR TKA will more closely replicate the knee kinematics and kinetics of healthy age-matched controls during stair descent, than will MR TKA patients. SR subjects (n = 12), MR subjects (n = 12), and age-matched controls (n = 12) descended four stairs affixed to force platforms, while 10 infrared cameras tracked markers attached to the body to collect kinematic and kinetic data. Both patient groups had improvements in stair descent kinetics and kinematics at the 1-year postoperative time point. However, SR TKA subjects were indistinguishable statistically from age-matched controls, while MR TKA subjects retained many differences from controls. Similar to previous reports for level walking, the SR knee design performs closer to healthy controls than MR knees during stair descent. This study demonstrates that patients who receive SR TKA have more improved kinematic normalization during stair descent postoperatively than those who received an MR TKA.
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