I'm not on Tysabri, but I know several MS patients who are or were and the positive effects were amazing. One woman I know has been on it much longer than advised, but she refuses to give up on it because she could hardly walk before Ty and she is doing so very well on it.
Steroid use in the long term destroys organs…so many neuros are reluctant to use it very often. I've only had one set of infusions from mine since starting with him 4 years ago, whereas the neuro before him had me on monthly infusions, which shocked my present neuro..
Also, the pain may be caused by spasticity…are you on muscle relaxants like zanaflex, baclofen or clonepam? It might help reduce the tightness and pain.

I hope that once you're on Ty you'll notice an improvement. MS can be very challenging to say the least...