Hi there....

I guess when we hear "pain up or down stairs" we think patellofemoral. But I believe you need to try and really reproduce his pain with special knee tests. It sounds like it is bothering him alot and if he has constant pain and he feels it deep and behind his knee, I'd tend to think more knee joint dysfunction (?Wikipedia reference-linkmeniscus/?OA). Another good point someone made is to get a good history!!

If you are confident it's patellofemoral, I'd agree with the other replies regarding management.

All the best as you nut out your patients