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Osteochondrosis lesions of the lateral trochlear ridge of the distal femur in four ponies
  1. L. C. Voute, BVSc, PhD, CertES(Orth), MRCVS1,
  2. F. M. D. Henson, MA, VetMB, PhD CertES(Orth), CertEM(IntMed), MRCVS2,
  3. D. Platt, BVSc, PhD, CertVR, DEO, FRCVS3 and
  4. L. B. Jeffcott, BVetMed, PhD, DVSc, MA, VetMedDr(hc), FRCVS4
  1. Weipers Centre for Equine Welfare, Division of Large Animal Clinical Sciences and Public Health, School of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow G61 1QH
  2. Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES
  3. Equine Direct Veterinary Services, Woodlands, East Hanningfield Road, Butts Green, Sandon, Chelmsford, Essex CM2 7TF
  4. University Veterinary Hospital, Faculty of Veterinary Science, University of Sydney, 410 Werombi Road, Camden, New South Wales 2570, Australia
  1. E-mail for correspondence lance.voute{at}

Lesions of the lateral trochlear ridge (LTR) of the distal femur were investigated in four pony or pony cross horses. The animals were all geldings and were six to 15 months of age. Lesions were bilateral in three ponies and unilateral in one. Femoropatellar joint effusion and lameness were present in two ponies; clinical signs were absent in the others. The proximal LTR was affected in all four animals. The radiographic appearance of the lesions was a subchondral defect containing mineralised bodies. Arthroscopic and postmortem examination findings included an osteochondral flap, a fissured or irregular articular surface and a smooth surface overlying focally thickened cartilage that extended into subchondral bone. Thickened articular cartilage was a histological feature of all the lesions. Among the other histological features, the most common were chondronecrosis, chondrocyte clusters, phenotypically abnormal chondrocytes, horizontal fissures at the osteochondral junction and retained blood vessels. The signalment of the four ponies, their clinical signs and the pathological features of their lesions were consistent with osteochondrosis of the LTR in horses. The use of multiple criteria was considered to be important in making a specific diagnosis.

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