EE notified supervisor of pain in shoulder in Dec. 2016. EE had noticed pain in shoulder that was bearable prior to that. Had surgery on shoulder in 2011. Notified supervisor of increased shoulder pain after work in the shop but thought it'd go away given some time. IE has been maint. mechanic for 5 yrs, did outby work for 2 yrs & CM production for 6 yrs prior to that.