Preoperative and postoperative joint motion in chihuahuas with Grade III medial patellar luxation: A kinematic and goniometric analysis

Medial patellar luxation (MPL) is a common orthopaedic disorder in dogs, resulting in stifle instability and altered pelvic limb biomechanics. While its effects on stifle function have been extensively documented, the influence on adjacent joints and the course of biomechanical recovery following surgical correction remain poorly characterized. This study aimed to evaluate active (AROM) and passive (PROM) range of motion in the stifle, hip, and tarsal joints of Chihuahuas with Grade III MPL using two-dimensional kinematic and goniometric analyses. Seventeen client-owned Chihuahuas were enrolled, comprising ten MPL-affected dogs and seven clinically healthy controls. MPL dogs underwent surgical correction, and joint motion assessments were performed preoperatively and at 2, 4, 6, and 8 weeks postoperatively. Significant reductions in stifle AROM and PROM, particularly in extension, were observed in the MPL group compared to controls, indicating functional impairment. Compensatory increases in hip and tarsal AROM were also detected preoperatively, suggesting biomechanical adaptation. Following surgery, stifle AROM progressively improved and approached control values by week 8, whereas stifle PROM remained consistently reduced. Temporal changes in hip and tarsal AROM suggested early compensatory adaptations, which gradually resolved as stifle function improved. However, persistent stifle PROM limitations underscore the need for early, targeted rehabilitation. A multimodal strategy addressing both primary joint dysfunction and compensatory changes is essential to optimize recovery. Baseline joint motion data may serve as valuable benchmarks for evaluating surgical outcomes and guiding individualized postoperative care.