Bone oedema-like lesions at the enthesis of DIPJ collateral ligaments: MRI findings, management and outcome

Bone oedema-like lesion is characterised by hyperintense signal in short tau inversion recovery (STIR) sequences on magnetic resonance imaging (MRI). Bone oedema-like lesions involving the enthesis of the collateral ligament (CL) of the distal interphalangeal joint (DIPJ) have not been investigated as a cause of lameness. This pattern was detected using low field MRI in nine forelimbs of eight horses. Lesions were found in the medial and the lateral collateral fossae of the distal phalanx in five and four feet; the lateral fossa of the middle phalanx was also abnormal in one foot. The STIR signal was graded as ‘severe’, ‘moderate’ and ‘mild’ in two, two and five feet, respectively, predominantly involved the dorsal two-thirds of the fossa. The lesion was the only pathology in six feet, while in three, the ipsilateral CL presented abnormalities. Follow-up MRI was available for two horses revealing a reduction in STIR signal. Five horses resumed a lower level of athletic activity, while three returned to the same or a higher level. Bone oedema-like lesion at the CL enthesis is a potential cause of lameness even if the CL appears normal. The prognosis is good, although further studies with a larger number of horses are required.