So, when I was exercising today, I was lying on my back with my legs bent. I was slowly raising each each foot and bringing the knee slowly back towards my chest. I happened to have my thumb slightly pressing against the area where the leg meets the hip (basically the hip joint) and noticed the second I moved my left foot off the ground, I felt the muscle (or maybe it was a tendon) really tense up (without pain though). It would remain tense throughout the whole movement. If I did the same movement on the right leg, I felt hardly any muscle/tendon tense up. There was a VERY noticeable difference between the left and right leg in this regard.

Does this say anything about the pain I'm having with certain movements? It's like the left leg is very week and is really needing to tense up the muscle to lift my foot off the ground and move my bent leg back towards my chest.