There is a large cord I can see and feel on the lateral (outside) part of my knee and I'm wondering what it is, as it hurts sometimes. Does anyone know what it is? I think it is the LCL, the IT band or the hamstring, but not sure which, does anyone know? I took a picture of it:
I think that's your biceps femoris, as it connects to your lateral hamstring tendon. Posterior view of your leg (looking at your leg from behind). You'll note the vastus lateralis (huge outer section of your quad) is on the same side, so we're talking the outer (lateral) side of your leg.
If it hurts, I would consider tendinitis. Tendinitis in particular can take a long time to heal and "working through the pain", which you can often do with small muscle damage, is really just going to aggravate tendinitis. Often the best plan is complete rest of the area, which should give you ample to time to figure out what problem caused it (insufficient strength, imbalanced muscles, over training, etc).