I went to a PT and was diagnosed with IT band syndrome. It seems to be improving and I'm running again. My question is this...Is it typical to be able to run a certain distance (in my case 4 miles) then my knee starts to feel "loose" or "weak" followed by some pain?

I had ACL surgery on that knee so I thought I had reinjured it until going to the PT. It's just strange that the only pain I feel in my IT band is where it connects at the knee. Is the "loose" feeling due to the IT band becoming inflamed during a run so it doesn't support the knee as well?