This case provided an opportunity to differentiate between an aggressive and nonaggressive arthropathy. Successful candidates (approximately 90%) earned almost all case points while unsuccessful candidates earned some (<70%) points.

• In this case 2 standard projections of a canine stifle were provided.
• Most candidates identified soft tissue distention, periarticular osteophytes and subchondral lysis of both the femoral and tibial condyles of the stifle joint.
• Few candidates addressed the severe loss of joint space width.
• Very few candidates mentioned the size of the popliteal LN on the lateral projection.
• Many candidates incompletely described the metallic surgical implants.

All candidates appropriately listed both septic arthritis and joint or soft tissue neoplasia as appropriate differentials. Unsuccessful candidates, in addition to incomplete descriptions, rank-ordered the differential diagnoses inappropriately. The candidates were expected to appropriately conclude that the aggressive changes were related to the previous surgery as the most likely differential (septic arthritis).

For further testing candidates were expected to apply local and systemic testing to confirm an infection and stage neoplasia. Few candidates included fine needle aspiration of the draining lymph nodes as part of their testing. Comments from candidate almost always included possible therapies, but no additional points were provided for that portion of their answers.

In conclusion, the vast majority of the candidates described the majority of the findings and appropriate rank ordered the logical differential diagnosis. Similarly, most candidates concurrently did not mention joint space width or popliteal LN size. This case had very high pass rate, but candidate performing poorly on this case rushed through the description and inappropriately ordered their differential diagnoses.