Dislocated hip (coxofemoral luxation)
This usually occurs as a result of trauma such as a fall causing the femur to come away from the hip joint and move upwards. In some cases the ligament that holds the joint together can rupture (round ligament rupture) with the femur not moving out of place.
Signs
The affected leg will appear shorter and the horse will stand with the toe and stifle pointing out and the hock pointing in. The affected animal will initially show a severe lameness. In cases of round ligament rupture the limbs will be the same length.
Diagnosis
The clinical signs may be enough to make an initial diagnosis, however, x-rays are required to confirm this.
Treatment
Surgery can be performed to replace the femur, however, the animal will not achieve soundness to be ridden and breeding soundness is the best that can be hoped for.
All cases end up getting degenerative joint disease (arthritis) as the joint is still unstable.