This is a question for the orthopedists or primary care doctor
who requested the MRI
. It is certainly possible that the pain you have been having in your knee is related to the sensations you are having in your foot. The nerves that provide sensation to the the foot have to move from the spinal cord in the lower back all the way down to your foot, and there are conditions in which a nerve can be pinched or irritated behind the knee. When this happens, a patient may experience neuropathic pain, similar to the "pins and needles" sensation you describe.
You don't mention exactly what symptoms (or possible injury) led you to undergo a knee MRI and physical therapy, but the fact that you are having trouble with the knee does suggest that your two symptoms could be related. In this situation, the best thing to do would be to start with the orthopedists or primary care physician who evaluated you for the knee problem and ordered the MRI. He or she will be able to help determine if the information from the MRI provides an anatomic explanation for the parasthesias you describe. In addition, your doctor can do a more thorough neurologic exam of your leg to determine if there are any motor deficits, changes in reflexes, and specifically map out which parts of the foot have sensory deficits. If necessary, you can be referred to a neurologist
to further evaluate you as needed. Hopefully your foot will stop "falling asleep" soon!