On 4/16 EE had filled water truck & turned to walk away. His boot stuck in grate; his body turned but lower part of leg didn't. EE noticed pain & swelling. Was taken to ER & released to work, but was working with discomfort. Diagnostic scoping of left knee was done 6/29 during his 7 days off. On 7/5 employee reported to work with restrictions making this incident reportable.