Timing of Wikipedia reference-linkcruciate ligaments reconstruction is controversial, traditionally, surgery performed as soon after the injury; however, there is some evidence that delaying of surgery may decrease postoperative risk of arthrofibrosis. But most important is condition of the knee at the time of surgery. The injured knee should have no swelling, have full ROM, and person should have normal gait(the main reason that he's have pain in the other knee probably is poor gait control-he's putting more weight on uninjured knee).Rehabilitation should commence immediately after the injury(the aim of preoperative management is reducing the pain,swelling and inflammation) including interferential stimulation, ultrasound,TENS,strengthening exercises for quadriceps,hamstring,hip extensor, abductor and calf muscles.Pain free ROM exercises should also be performed.
It's necessary that he's have rehabilitation program after surgery as well.
Hoped this is helpfully to you
Regards Nale.