According to the ACR criteria for knee OA, how many clinical and radiographic findings are needed out of 3?

• A. 2 out of 3
• B. 3 out of 3
• C. 1 out of 3
• D. 0 out of 3

Answer: (C)

In this criterion, the idea is that knee OA is diagnosed by combining clinical symptoms with radiographic signs, using two parallel sets of findings. There are three clinical features that can support the diagnosis and three radiographic features that can support it. The minimum threshold being tested here is that you don’t need all three clinical features or all three radiographic features; you only need one from each domain to contribute toward the diagnosis. So, out of the three possible clinical findings, one is enough, and out of the three radiographic findings, one is enough to meet the criterion.

In real practice, the ACR criteria are more specific, requiring knee pain plus three of six clinical features, or radiographic OA evidenced by osteophytes with additional features. The item here is presenting a simplified threshold to emphasize the combination of clinical and radiographic information rather than relying on a single type alone.