Legg-Calvé-Perthes disease: radiographs and diagnosis
7-month-old Yorkshire Terrier with progressive right pelvic limb lameness, pain on hip extension and thigh muscle atrophy. On the ventrodorsal radiograph the right femoral head shows mottled radiolucent areas, flattening and irregularity; the joint space is widened and the femoral neck is thickened.
What is the most likely diagnosis?
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A. Avascular necrosis of the femoral head (Legg-Calvé-Perthes)
Correct. It affects small and toy-breed dogs aged about 4–12 months, almost always unilaterally. Mottled lysis, femoral head collapse and neck thickening are typical.
B. Hip dysplasia
Dysplasia causes subluxation, a shallow acetabulum and osteoarthritis, and is far more relevant in large breeds. It does not explain mottled lysis of the femoral head.
C. Medial patellar luxation
It is common in the same breeds and may coexist, but it involves the stifle. It does not cause femoral head changes.
D. Capital femoral physeal fracture
It shows a separation line through the physis with epiphyseal displacement, usually after trauma. Here the change lies within the epiphysis.
lightbulb Key takeaway
Also examine the stifles: medial patellar luxation may coexist and confuse localisation of the lameness. Early on, radiographs may be normal or show only joint space widening; repeat them if signs persist. Usual treatment is femoral head and neck excision, with a good prognosis.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.