Medial femorotibial and femoropatellar articular cartilage delamination following intra‐articular therapy with triamcinolone and gentamicin in five yearlings

Summary Subchondral lucencies (SCLs) of the medial femoral condyle (MFC) are a cause of lameness in young horses, potentially affecting future athletic performance. Due to the widespread use of pre‐sales screening radiographs for Thoroughbred weanlings and yearlings, these lesions are frequently identified at various stages of progression without the manifestation of clinical signs. Treatment for horses without lameness or effusion is not recommended as most do not develop clinical signs. Conversely, conservative treatments, such as reduced exercise and the use of non‐steroidal anti‐inflammatory medications or intra‐articular therapies, typically yield suboptimal outcomes in clinically significant SCLs, and these will frequently be presented for surgical intervention. This report documents five yearling horses with MFC SCLs that had received speculative intra‐articular (IA) injections of 10 mg triamcinolone acetonide (TCA) and 40 mg of gentamicin sulphate (GS) into the medial femorotibial joint (MFTJ). Treatments had been initiated by the attending veterinarians based on their own circumstantial impressions that treatment might help improve some radiographically observed MFC SCLs detected on weanling screening radiography. All cases in this series became acutely lame on the treated limbs, developing marked effusion of both the MFTJ and the femoropatellar joint (FPJ). Clinical assessment and synovial fluid analysis confirmed that all cases were non‐septic. Due to the development of clinical signs, surgical management was advised. Before surgery, affected joints did not show additional radiographic changes compared to initial radiographs. While examining the MFTJ and FPJ using standard arthroscopic techniques, large areas of detached and partially detached cartilage were present on the caudal aspect of the distal patella, the lateral and medial trochlear ridges and the central articular surface of the MFC. These lesions had the appearance of acute delamination of the articular cartilage, exposing an underlying, pale, avascular subchondral bone plate below. This case series is the first to report iatrogenic articular cartilage damage in the MFTJ and FPJ of thoroughbred yearlings treated for early MFC SCLs with recommended therapeutic doses of IA TCA and GS. This case series demonstrated that IA injections of TCA and GS in juvenile horses with MFC SCLs can have negative effects on articular cartilage. We propose that IA corticosteroids should not be used in young horses with MFC SCLs on radiographs but without clinical signs and owners should be apprised of this potential complication. Further research into the potentially negative effects of IA corticosteroids on the cartilage of juvenile horses would be appropriate.