Assessment of a goat model of posterolateral knee instability.

The development of an in vivo animal model of posterolateral knee instability is desired for devising effective interventions for this injury. Sequential sectioning of the popliteus tendon, lateral collateral ligament, and lateral capsule was done in cadaveric goat knees to create knee joint instability, followed by in vivo studies (Studies 1 and 2) of 7 and 3 months duration, respectively. In Study 1, the popliteus tendon and lateral collateral ligament were sectioned; in Study 2, these structures as well as the lateral joint capsule were sectioned. Biomechanical testing and histological assessments were done to determine the severity of the instability and the morphological changes. Sectioning the lateral collateral ligament and popliteus tendon (Study 1) resulted in a significant increase in varus instability at 90 degrees . Sectioning the lateral collateral ligament, popliteus tendon, and lateral capsule (Study 2) resulted in significant varus instability at 30 degrees , 60 degrees , and 90 degrees , and significant internal-external rotation at 60 degrees and 90 degrees ; however, the lesions of osteoarthritis in the operated knees were similar to those in unoperated control knees. This study confirms that posterolateral knee instability can be created in a goat model, but we were unable to demonstrate lesions of osteoarthritis that were of sufficient severity to allow evaluation of disease reduction in future intervention procedures. Future studies will determine if further manipulation of the model results in sufficient morphological changes to allow its use in the assessment of intervention strategies.