Hello, There can be many reasons for him not being able to walk properly . There may be severe arthritis in knees or may be something else its difficult to say without seeing him. Would sugest to visit a physiotherapist who can assess him and know what has happened to him and why he cant walk. Physiotherapy is not expensive .you may search for a charatable trust in your area as many places charatable physiotherapy clinics are there it may solve your problem of finance . Dont worry he will be soon walking well.