Hi,
Since he has certain acute and chronic (degenreatvive arthritis) changes, the surgery would probably lead to a slightly prolonged recovery. While I am unable to examine him and thus give a precise estimate, your description makes me feel that the recovery period would be atleast a couple of months if not longer.
The rehab options mentioned in the previous reply should all be undertaken under the care of an expert physio to make him get back to his feet ASAP,
Please remember to accept the reply if you find it useful. A BONUS and a positive rating would be duly appreciated,
regards
Dr. Gupta