Shortness of one leg- High CPK levels

Hello Dr.

My four year child has left leg shorter than the right by one cm. We found out this when he was around two years old.
His CPK levels were found to be higher: 167 U/L (prescribed normal range for Male 15- 130 U/L). We also did his Electro Mayo Graphy / Nerve Conduction Velocity. The doctor diagnosed him of 'Gastrocnemius Congenital Contracture Left Side' and told us to do some stretching exercises on his left ankle and get it checked every year.

I wanted to know what does high CPK level means? How can they be brought to normal levels? What will happen to his leg length? Is there a remedy for his short leg? If his leg remains short when should we do the correction and what correction is needed? I am very concerned about this situation please advise.

Thanks