I’m writing this in the hope that someone googling symptoms will get a hit and my experience will be useful.

If you find one of your legs is dragging a bit and seems weak but you aren’t in pain you should consider getting an MRI or see a good physio. I just had 3 months of various issues with my left leg without any pain before consulting with a doctor. He suggested I suspend cardio because he suspected muscle damage in the leg and subsequently  I did a double gym session hitting my back. The result was that I ended up with classic Sciatic pain:  sharp, shooting pains in my leg that left me unable to stand at all for around 24 hours and substantial pain and problems sitting more than half an hour in the following weeks.

Fortunately the next Doctor I saw was on the ball and quickly ordered an MRI. The upshot is that within one month of seeing the second doctor I went from no diagnosis at all to having just had surgery because I had a herniated disc. The surgery went very smoothly and the recovery has been relatively pain free.

The moral of story, however, is to get yourself seen to as quickly as possible if  your case matches mine as the weakness can be permanent after more than a few weeks of nerve compression. Only time will tell what the situation is for me and what functionality I will have in the long term.

If you can’t get an MRI try visiting a physio as mine diagnosed the problem correctly prior to seeing the MRI results. He did the one test which the doctor who suspected muscle damage didn’t try: he got me to lift myself on each foot. I could lift myself tens of times on my right foot but couldn’t lift myself even a single time on my left foot. He also determined I couldn’t feel anything on parts of my left foot. Your case might be different so see somebody with appropriate medical training ASAP.