Lateral luxation of the patella is generally a rare, inherited condition in foals and American Miniature horses that is caused by a recessive gene. In adult horses, luxation of the patella is unusual and likely to be traumatic in origin.
Lateral patellar luxation is more common than medial patellar luxation and might be more likely in horses or foals with hypoplasia of the lateral trochlear ridge of the femur. The condition can be unilateral or bilateral and varies in severity from intermittent luxation that readily reduces to persistent luxation that cannot be reduced.
Foals with severe patellar luxation are unable to extend the stifle, so they adopt a characteristic crouching position. If the condition is less severe, affected horses of any age might be reluctant to flex the stifle and thus will demonstrate a stiff hindlimb gait. Diagnosis can be confirmed by radiography.
Although a number of surgical treatments for patellar luxation have been described, the prognosis for adult full-size horses and for horses with concurrent osteoarthritis is poor. The prognosis for athletic function in foals might be slightly better. The prognosis for American Miniature horses is considered to be favorable after surgical treatment.
For More Information
Also see pet owner content regarding disorders of the stifle in horses.
