Employee reported accident on 8-15-08. On 8-8-08 Employee stated at end of shift that his knee was sore from working on his knees for two 12 hour shifts in a row. He said that no special event took place but that his knee became sore. He thought that it was just sore from constantly working on his knees. On 8-15-08 he felt that it wasn't improving and needed to see the nurse.