Hey Bonsall. This is our problem.
I've been dealin' with it since I was 12. This is much more common in taller individuals who have a quick growth spurt (yep, that's me). Damn you genetics!
Had to quit running because of it. Now the problem has found me in cycling. Gonna start some mild stretching again. I've been slacking for quite some time with the stretching and I paid the price.