Employee stated that they were climbing up onto the dozer to work on the engine. As they did, they felt a pop in left knee. They experienced extreme pain in the knee as they attempted to walk on it. Went and got checked. Missed work on 06/24 and returned on regular duty on 06/25. Went to ortho on 06/27. Returned to work on regular duty on 06/30. Lost 2 days work.