There's a new one out, too, just for patients with low back pain. It combines questions from all three of these tools and appears to be a valid scale. It's easy-to-use and does a good job assessing patient's function. It's called the Low-Back SF-36 PF(18).
Ask your doctor or physical therapist about using some type of before and after testing to mark your progress.
Megan Davidson, BAppSci, et al. A Low Back-Specific Version of the SF-36 Physical Functioning Scale. In Spine. March 1, 2004. Vol. 29. No. 5. Pp. 586-594.