Talk to Rheumatologist on A Diabatec Father With Knee Fracture/crack

My father is broken his knee joint of left leg while slipped. He has his knee joint with crack and showing gap. There is some swelling also. Doctor suggests surgery but we are reluctant because he is suffering from diabetes from last 39 years. Normally, the wounds or bruise he gets takes months to recover with ultra care and treatment. So, we are worried very much from surgery but at the same time request your panel for a treatment as we can't see him in this condition. Thanks