Just to be clear, there is a big difference between a dislocated knee and a dislocated patella. Your patella is referred to in lay-man's terms as your knee cap.
I'm not saying it is impossible to dislocate the knee - meaning the bones in the upper leg and/or lower leg separate from the joint and not also suffer structural damage. But I think it is unlikely. If he has no damage, it was likely a patella dislocation.
I suffered a dislocated knee (not patella) while playing soccer in college. Some of you may have heard of the "trifecta" of knee injuries - often referred to as blowing out your knee. I accomplished the "quadfecta". It was the trifecta plus fractured the head of my femur. Torn ACL, Torn LCL, Torn Miniscus + femur fracture.
If the report on the board is accurate that he has no structural damage then halleluiah. That is a positive first report and is encouraging for his return to the mat in the post season.