EE was replacing hanger bearings below Stone Packaging on knees for a few hours on 4/8/21 and was sore the next few days. As time went on the knee felt better. On 5/18/21 EE had to replace the springs on the pellet mill. The next week the knee felt worse, EE had to limp and could feel fluid building on knee. On 5/28/21 the employee decided to get fluid drained making it reportable.