I suffered a tibial plateau fracture 16 years ago while playing football (OT fell on my knee from the side while I was pass blocking) - I feel your pain, JJ...
When he will be able to return will depend on whether it's a clean fracture or if his tibial plateau got shattered in pieces (like mine was). If it's the latter and he needs reconstruction of the bone (like I did) then it might take up to a year I guess.