Legg-Perthes disease is not particularly difficult for a veterinarian to diagnose. However, the symptoms of Legg-Perthes disease can mimic those resulting from other causes of hind limb lameness, such as patellar luxation, hip dysplasia, trauma/injury/fracture of the femur or pelvis, degenerative joint disease and septic arthritis of the hip joint, among others.
Most veterinarians presented with a limping dog will get a complete history from the owner and then conduct a thorough physical examination. Of course, when a patient is lame, the veterinarian will carefully examine, palpate (feel) and manipulate the affected leg and surrounding area to assess pain, reflexes, bone integrity, inflammation, swelling, temperature/heat and the like. An initial database of blood work (complete blood count and serum biochemistry profile) and a urinalysis are routinely performed as well, to assess the overall health of the dog’s primary organ systems and to look for evidence of infection. If Legg-Perthes disease is the only abnormality in the dog, the results of these tests will be normal.
If the physical examination localizes the site of pain or injury to the hip area, the next nearly universal diagnostic step is to take radiographs (x-rays) of the pelvis, both femurs (the long thigh bones) and both hips. This is important, even if only one side seems affected, so that the veterinarian can compare the radiographic images of both femurs and hips. Early in the course of the disease, radiographs may only disclose a slight widening of the space between the ball of the femur and the pelvic socket (the acetabulum), together with changes in the density of surrounding bone. As the disease progresses, these radiographic changes become more dramatic and almost always become diagnostic of Legg-Perthes disease. The changes can include severely abnormal bone density, irregular shape of the femoral neck and head, fractures, bone fragmentation and other evidence of degenerative joint disease.
Advanced radiographic imaging studies, such as magnetic resonance imaging (MRI), computed tomography (CT/CAT scan) and/or nuclear scintigraphy, typically are not required to diagnose Legg-Perthes disease in dogs. The age, size and breed of the animal, together with the history, physical examination and radiographs, should be all that is needed to make a definitive diagnosis.
As with most diseases or disorders, it is best if Legg-Perthes disease is diagnosed early in its course. Treatment and management are all that much easier before the problem has become chronic.