Why Do My Shin Muscles Ache After Exercising?

hi i had a spiral break of the tibia in 2007,which i was placed in cast for 3 months. 1 year later i broke the same leg in the same place which led to me having a internal fixation of plates and screws, 2 years later i am still getting pain in the shin muscle whenever i exercise, which causes me to limp for a few days after. could you please giv me an explanation of what could be causing this?