so i'm a 17 year old headed towards the tail end of a 3x5 linear progression based around starting strength. Progress has been fine up until lately, when i've had to stop squatting due to pain on the outside of my left hip (looking at anatomy charts, i think it's the tensor fasciae latae if that helps). Basically sinking past 90 degrees triggers pain.
right now it hurts to lift my left knee and then rotate it towards 10 o'clock. My flexibility is pretty solid (i'd been squatting 25-35 deg past 90 up until now) and at the time my mobility wasn't fantastic-i had stopped doing mobility drills as frequently, and i noticed that with my ankles, my knees were barely tracking past my toes when i squatted. I
don't have a video of my form, but the best i can describe is that it is a high bar squat, feet about 3 inches past shoulders (maybe a little more) dropping pretty straight down. I understand that this isn't very helpful, but it's the best i can do right now.
i should probably add that deadlifting doesn't hurt, and i've a history of poor left hip mobility as a result of my throwing mechanics in baseball. That said, i did spend the end of my summer and early fall working often on mobility, and by mid fall my left hip was in a good place in that regard.
i'm wondering if anyone has something they can contribute as to a potential cause, what i can do, and future prevention. Thanks in advance.