Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
Disturbances of gait associated with injuries to the stifle area, or to faulty conformation leading to stifle lamenesses are common in the smaller breeds of horses. Miniature Shetland ponies in particular seem to be especially prone to stifle lameness. Most authorities discuss luxations of the patella as occurring rather infrequently as a cause of lameness, except that some indicate that it may be common in colts with poor conformation or those fed a poor ration and , that these animals will "grow out" of the condition as they mature. However, spontaneous recovery is not frequently seen in the smaller breeds, but instead the condition in most cases progressively becomes worse if not treated.
Lundvall, R. L.
"Tibial Injuries and Recurrent Patellar Luxation in Young Horses,"
Iowa State University Veterinarian: Vol. 19
, Article 4.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol19/iss2/4