Investigation of Canine Hamstrings and Quadriceps Muscle in Cases of Cranial Cruciate Ligament Rupture

To evaluate the influence of the cruciate-deficient canine stifle joint on the hamstrings and quadriceps muscle by means of electromyographical and histopathological examinations, forty dogs with rupture of cranial cruciate ligament were examined. Dogs were divided into two groups according to their duration of lameness. Spontaneous electrical activity was found mainly at the semitendinosus muscle in both groups. The thigh muscles showed a trend towards the appearance of spontaneous activity, preferentially in the muscle of the diseased limbs rather than the healthy limbs. Dogs in group 2 tend to have more severe electromyographical changes than dogs in group 1. Major findings on histopathological evaluation were single fiber atrophy and signs of degeneration and regeneration. Unilateral rupture of the canine cranial cruciate ligament induces different electromyographical and histological alterations in the hamstrings and quadriceps muscle of the affected and contralateral healthy limb. These alterations could be caused by hypo activity and an altered anatomical axis of the diseased limb and increased overload of the healthy limb.