Internal rotational laxity of the stifle is increased in dogs predisposed to or affected by medial patellar luxation or cranial cruciate ligament disease.

Objective: To report and compare the range of stifle rotation in dogs predisposed to, or affected by, medial patellar luxation (MPL) or cranial cruciate ligament disease (CCLD) with that of Greyhounds.

Methods: Greyhounds (negative controls), sound dogs of breeds predisposed to MPL or CCLD, and dogs with MPL or CCLD were enrolled in this clinical prospective study between December 5, 2022, and October 27, 2023. They underwent orthopedic examination and goniometric measurements of tibial torsion and stifle rotation, flexion, and extension. Limbs were classified as having low risk for, being predisposed to, or being affected by stifle disease. Body condition scores, tibial torsion, stifle rotation, flexion, and extension were compared between groups of limbs.

Results: Data were collected on 208 limbs (104 dogs), classified as 48 controls, 37 limbs predisposed to MPL, 47 limbs predisposed to CCLD, 44 limbs with MPL, and 32 limbs with CCLD. Internal rotation was greater in stifles diagnosed with MPL (median, 38.83°; IQR, 35.67° to 46.83°) or CCLD (median, 32.17°; IQR, 25.67° to 35.67°) than in controls (median, 12.0°; IQR, 10.33° to 13.33°). Similar results were obtained when sound limbs predisposed to MPL (median, 32.22°; IQR, 27.67° to 35.67°) or CCLD (median, 32.17°; IQR, 25.67° to 35.67°) were compared to those of Greyhounds.

Conclusions: Internal rotation exceeded that of control limbs by approximately 20° in stifles predisposed to or affected by MPL or CCLD.

Clinical relevance: These findings provide evidence of an association between rotational laxity and the presence of or predisposition to MPL and CCLD in dogs.