Progression of femoropatellar osteochondrosis in nine young horses. Clinical, radiographic and arthroscopic findings.

The research study investigated the progression of femoropatellar osteochondrosis, a joint disorder, in nine young horses and reported on clinical symptoms, radiographic changes, and outcomes of arthroscopic surgery.

Study Purpose and Methods

• The purpose of this study was to examine the progression of femoropatellar osteochondrosis (OCD) in young horses that are less than a year old. OCD is a developmental disorder that affects the cartilage and underlying bone within joints, potentially causing pain and lameness. The study analyzed clinical symptoms, radiographic (X-ray) findings, and arthroscopic surgery results.
• The sample group consisted of nine young horses with a history of hindlimb lameness due to OCD. Among them, eight had the condition in both hind limbs (bilateral) and one in a single limb (unilateral). The duration of the lameness history varied from 2 to 12 weeks.

Clinical and Radiographic Observations

• Two primary clinical signs were observed: Distention (swelling due to fluid build-up) in the femoropatellar joint, and lameness in the hind limbs. For some, radiographic evidence of lesions was either not visible or extremely subtle at the onset of these clinical symptoms. However, the lesions became clearly identifiable in X-rays taken 4 to 24 weeks post-onset.
• The authors highlight a key finding: the full extent of the radiographic lesion can take several weeks to develop, suggesting that lesions of OCD in the distal femur can progress in foals younger than 9 months once clinical signs appear.

Arthroscopic Surgery and Follow-Up

• Arthroscopic surgery was performed on the horses once changes were clearly visible in the radiographs. In these surgeries, common findings included osteochondral “flaps” on the proximal lateral trochlear ridge of the femur. These lesions were larger than what the initial radiographs indicated.
• Eight of the nine horses continued to be used for their intended purpose either in racing or dressage, or for pleasure riding. However, one horse required a second surgery as it developed similar lesions on the opposite stifle joint and was eventually euthanized two months later due to persistent lameness.

The study highlights the critical need to monitor horses showing early clinical signs of OCD closely, as both the presence and the extent of the damage to the cartilage and bone may not be immediately visible via early radiographic imaging.