Trouble extending leg (Read 459 times)

My right leg has always been a bit on the 'tight' side. Here in the last few weeks, I've noticed when during stretches that I'm not able to fully extend my leg. There's a pull/pain on the underside/side of my knee. If I massage it, it releases the tightness and then relaxes a bit but I'm not able to fully straighten my leg. I've done the google thing and have yet to come across anything remotely close to what I've got. Most articles discuss runner's knee or meniscus tears but there isn't really any pain in my actual knee. I can pinpoint the pain to what I'm assuming are tendons that run on the side and underside of the knee. Has anyone experienced this at all? I can still run. It doesn't stop me running but when sleeping or lying down, I have to keep that leg bent. Doing floor exercises,the right leg must stay bent to avoid the pain. It does tend to radiate down the side of my calf if I try to force the stretch. Thanks

Thank you!