Employee was carrying a 5 ton chain hoist (approximately 50 pounds)downstairs. He was not using the handrail and was stepping in a sideways motion to ""baby"" his left knee that was injured previously. Initial doctor visit and x -ray on 3/17/11. Follow up and referral to second doctor on 3/28/11. MRI results on 4/12/11 of a tear in the acl.