Been going to gym for 3 months, working with a pt on strength based stuff. Starting as a total newbie and not I can seen tiny muscles 
But I keep getting really stiff in my heels/Achilles. So if I've been sat at my desk for a bit and get up or first thing in the morning it feels very tight and stiff and I hobble. It's on both sides but worse on the left.
For full info I have a dodgy left knee which I have to be very careful about and as a result feel many more niggles on that side as I try to protect myself a bit so sure that doesn't help.
Any ideas? I am a couple of stone overweight so I am sure that doesn't help but pt says my form for all my leg stuff is good.....