Tendonitis of the deep digital flexor tendon (DDFT) in horses is a newly recognized cause of foot pain. Radiography and even ultrasonography have failed to detect abnormalities in this tendon, especially as it travels within the hoof capsule and attaches to the pedal or coffin bone. In an effort to improve the ability of practitioners to diagnose DDFT lesions within the foot, a study was performed to determine the incidence and types of DDFT injuries in horses with a history of lameness localized to the digit.

A group of 75 horses undergoing MRI for investigation of foot pain with no radiographic abnormalities was investigated by Sue Dyson, FRCVS, of the Center for Equine Studies, Animal Health Trust, Newmarket, U.K., and colleagues, in an effort to describe the lesion in light of the response to nerve blocks as well as ultrasonographic and nuclear scintigraphic findings.

MRI examinations identified 46 horses (61%) with lesions of the DDFT that could be considered a major contributor to lameness. Thirty-two horses (43%) had primary DDFT injuries, and 14 (19%) had a combination of DDFT and navicular bone problems. Information such as breed, type of work, and diagnostic findings was also gathered and analyzed. Findings were compared to those in horses with other types of lameness or poor performance.

No breed predilection was identified, but horses used for jumping tended to have lesions more often than horses of other disciplines (48% versus 36% of horses in other disciplines affected)