thigh/knee pain (Read 390 times)

so, last saturday near the end of my 18 mile run, I got a pain in the outside (but still front) lower thigh. It went away after the run and was fine for my runs the next few days, even a 14 miler on tuesday. On wednesday on an easy run it was back, and friday it was there again. It felt like someone was driving their knuckle into my thigh. Anyhow, it wasn't anything I was too worried about until today. The pain was back about 5 miles into my run today, and I ignored it and kept going, well, it worked its way into my knee turned into a sharp pain at about 14 miles and I was unable to even finish the run. it is now very tender in the initial spot and in my knee joint as well. I can walk alright, but trying to run just a few step and my knee buckles. If anyone has experienced this or has any advice for me it would be greatly appreciated. thanks in advance.