Peroneal paralysis results in paralysis of the muscles that flex the hock and extend the digits.
The peroneal nerve is the cranial division of the ischiatic nerve. It passes superficially over the lateral femoral condyle and the head of the fibula, which makes it vulnerable to external trauma or pressure from recumbency. An affected animal stands with the digit knuckled over onto the dorsal surface of the pastern and fetlock. The hock may appear to be overextended. In mild cases, the fetlock tends to knuckle over intermittently during ambulation; however, this may also occur if the animal is experiencing pain in the heels.
In severe cases, the dorsal surface of the hoof may be dragged along the ground, and sensation to the dorsum of the fetlock is often decreased. Testing of reflexes may demonstrate that hock flexion is absent, but stifle and hip flexion are normal. This would not be the case if the ischiatic nerve was involved.
Most cases resolve naturally. However, if the condition is associated with long periods of recumbency, care must be taken to avoid exacerbation of the initial injury.
Last full review/revision September 2015 by Paul R. Greenough, FRCVS