Static Coronal Plane Alignment of the Knee phenotypes are associated with distinct dynamic knee kinematics in advanced knee osteoarthritis

Abstract Purpose The purpose of this study was to determine whether Coronal Plane Alignment of the Knee (CPAK) phenotypes were associated with distinct rotational and translational knee kinematics during preoperative treadmill walking in patients with advanced knee osteoarthritis (KOA) awaiting total knee arthroplasty. Methods Bilateral knee data were collected from 160 patients; 292 of 320 knees with Kellgren–Lawrence Grade III–IV osteoarthritis were included after radiographic screening and classified using full‐length standing radiographs. During treadmill walking, flexion–extension, internal–external rotation, adduction–abduction, and anteroposterior, proximal–distal and mediolateral excursions were recorded with the Opti_Knee system. Maximum and minimum rotational angles and translational excursions, rotational range of motion (ROM), translational excursion, gait speed, step length and cadence were assessed. Common phenotypes were compared; rarer phenotypes were described. Results Mean age was 65.0 ± 6.9 years, and 108 patients (67.5%) were women. Phenotype distribution was Type I, 110 (37.7%); Type II, 32 (11.0%); Type III, 14 (4.8%); Type IV, 77 (26.4%); Type V, 35 (12.0%); Type VI, 12 (4.1%); Type VII, 6 (2.1%); Type VIII, 4 (1.4%) and Type IX, 2 (0.7%). Type V, with neutral arithmetic hip–knee–ankle angle and neutral joint line obliquity, showed greater flexion–extension ROM than Types I and II, smaller anteroposterior and mediolateral excursions than Types I, II and IV, and greater proximal–distal excursion than Type IV. Type I had a higher minimum flexion–extension angle than Types IV and V; Type II showed greater maximum anteroposterior excursion than Types I, IV and V; Type IV had less extension restriction than Type I but greater anteroposterior and mediolateral excursions than Type V. Rare phenotypes were heterogeneous. Conclusion Static CPAK phenotypes were associated with distinct dynamic knee kinematics in patients with advanced KOA. Preoperative gait assessment may complement static CPAK classification by providing phenotype‐specific dynamic kinematic information before total knee arthroplasty. Level of Evidence Level III.