Hi Tony and welcome. Your symptoms could be MS related, but I think you would be jumping the gun to pursue that right now. There could be very simple explanations for each of the three symptoms you mentioned. I would definitely wait to see if your knee gets better over the next few days or weeks. Like you said, it might be your back. Do you ever go to the chiropractor? Or a massage therapist? Perhaps you would get some relief that way if you tweaked your back.
Really, I wouldn't worry about MS at this time. I would make a note of these things in a journal or appt. book just in case you have other symptoms appear. Then you could give your doctor an accurate history of symptoms.
Best wishes!

Julie