(See Attached)EE was walking down the pipeline cross over stairs and when he stepped of the bottom step he felt a pop in his left knee.The knee began to swell and he had pain,could not put his full weight on knee.EE had prior knee surgery.Xrays taken,recomm. a brace.EE RTW 8/28 On 9/3EE felt knee pop on 9/6 sent him home EE missed work on 9/6.9/11 EE had MRI torn ligaments.