Been dealing with this for months now. I'm in my early 30's. Originally thought it was a cardiovascular issue related to some shortness of breath/heart fluttering I've been having as well. To be honest, it could be, but Doctor's assumed for the most part my heart fluttering was due to stress/caffeine intake.
It is certainly more closely related to when I'm running. I can't get passed 5 days in a row (4 miles a day) without this issue coming on. If I stop running for a week, it lingers, but gets much better/mostly gone as the days go by. When it happens, both my legs feel slightly swollen, tingling, tight. It is something that inhibits my running and eventually forces me to take days off every week. It always occurs with both legs and never just one. The feeling goes slightly passed the knee. Just sitting/standing at the office bugs it a ton. If I lay on the couch with my legs flat, the issue seems to fade away until I'm back up. No issues in the feet either.
This is something I've never experienced since I started running (ran in high, college, post). It abrubtly came about a year or so ago, and becoming much worse in the past 6 months. I have no other issues...just the feelings that I describe above.
Obviously, a friend mentioned compartment syndrome to me already. However, I have no foot drop issues, shin pain, etc. The sensation also goes to my lower quads, which didn't seem related to CS.
Any help would be great. Can't figure this thing out for the life of me.