If he's been stall bound for 5 months, his muscles could very well be atrophied, giving the appearance of lameness. There was an Arab at one of my work barns that tore a suspensory, and was on stall rest and various treatments including wedge shoes and poultices and meds, and I don't know what else, as he wasn't mine at the time, for roughly 6 months, and when he was finally turned out (sedated in a small paddock) he was so atrophied that he looked horribly lame. He needed the turnout to get the elasticity back in his muscles and ligaments. The owner and the BO were convinced after seeing him turned out a couple times that he would be lame for life, so the owner gave him to me. It was that or auction, as she was getting divorced and could no longer afford his care. We brought him home, pulled the shoes, gave him bute as needed, and let him have limited turnout. Another three months and he was sound as a buck, and being ridden W/T/C. He was never lame another day in his life. Faye is right, sometimes they just need time.
"Keep a leg on each side and your mind in the middle"