On April 12, 1945, a three day old Shetland filly was admitted into the Stange Memorial Clinic. The colt was born with contracted flexor tendons of all four legs, the condition being extreme in the rear legs. This congenital defect is not infrequent, although it is not commonly seen in thoroughbreds, or shetlands. It was formerly attributed to infection of the tendons in utero, but today it is believed to be due to a recessive genetic factor appearing in closely bred individuals.
"Contracted Tendons in Foals,"
Iowa State University Veterinarian: Vol. 8
, Article 12.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol8/iss2/12