One leg developing quite a bit faster than the other one

Hello,

So last night I noticed that my Bf's left leg is getting quite muscular and that his right one only showed slight improvements.

Now, some background information he does have limited movement in that leg so basically he can't stand on his toes or really work the calf muscle much because of it.

Now, usually when his not gyming its not immediately noticeable, but if his left leg continues at the pace its going then well it will become quite transparent. Its not that his left leg is all that great its just it does the exercises the way its suppose to and thus gets the results.

His tried everything he can think of and thus I'm asking here for some other ideas. He tries training the right leg a lot more than the left, but still the left out paces the right. I've suggested not working out the left leg till the right catches up, but that would mean stop working out the lower body really.

So, I'm asking here to those more experienced with various workouts to suggest anything they can think of to help the right leg along that kinda doesn't involved much raises, but still works out the calf. The thigh is okay, but the poor calf lol so yes thanks!

ps: He does squats a lot and tries to do the calf raises etc so more unconventional workouts that we might not have tried since his tried most of the recommended ones. I'm honestly not sure if you can work out the calf while being flat footed, but hey I might be wrong and no harm in asking.

PPS: I'd show you a photo lol, but don't want anyone to be blinded by his hairy legs lol, just trust me when I say it is noticeable when you look for it and since summer is here and its soooo hot he mostly wears three quarters that shows off the calf area so yes help please.