Developmental Lateral Patellar Luxation in Standardbred Yearlings: Understanding the Condition

Area of Science:

• Equine orthopedics
• Veterinary diagnostic imaging
• Equine sports medicine

Background:

• Developmental lateral patellar luxation is a condition affecting young horses.
• Femoropatellar dysplasia (FPD) involves abnormal development of the stifle joint.
• Osteochondral lesions in the lateral trochlear ridge (LTR) are associated with patellar maltracking.

Purpose of the Study:

• To determine the incidence of FPD in Standardbred yearlings.
• To describe the clinical and pathological findings of FPD.
• To link osteochondral lesions in the LTR to patellar maltracking in FPD cases.

Main Methods:

• Retrospective case series of Standardbreds under 12 months of age diagnosed with FPD (2017-2023).
• Review of medical records, including clinical examinations and radiographic findings.
• Analysis of incidence, age of onset, clinical signs, and radiographic abnormalities.

Main Results:

• FPD incidence was 6.4 cases per 1,000 foals.
• Clinical signs like patellar instability and joint effusion appeared between 3-9 months.
• Radiography showed abnormal patellar tilt, LTR osteochondral lesions, and other abnormalities in affected horses.
• Six horses experienced severe lameness, and four were retired; six cases led to euthanasia.

Conclusions:

• Femoropatellar dysplasia is a significant condition in Standardbred yearlings, with early clinical signs.
• The study confirms a link between patellar maltracking and osteochondral lesions in the LTR.
• FPD has a poor prognosis for racehorses, often limiting careers despite treatment.