Low back pain, which is frequently associated with intervertebral disc degeneration, is the most common cause of adult disability in the United States. Among active service members, the incidence of disc degeneration more than doubled from 2001 to 2010, with over 68,000 days of lost duty time attributed to disc degeneration.2 The most common location of chronic pain in Veterans is the spine. The incidence of back pain in the general public has remained relatively stable over the past decade, however, there has been more than a 50% increase in the number of Veterans diagnosed with back pain. The intervertebral discs are the largest avascular structures in the body, and therefore cells within the disc rely on transport from the small vessels in the adjacent vertebral endplate to receive nutrients and expel waste products. Despite the immense social and economic burden of back pain, the etiology of disc degeneration remains poorly understood. Because of the avascular nature of the disc, it has been speculated that poor disc nutrition characterized by reduced trans-endplate transport into the disc could contribute to the initiation and progression of degeneration. If a reduction in trans-endplate transport of nutrients and waste products is a primary contributor to the initiation and progression of the degenerative cascade, then enhancing disc nutrition may have a therapeutic effect. Physical therapy and exercise can be very effective in managing back pain for certain patients, yet it is not fully understood why certain patients respond to physical therapy and others do not, and what effects such interventions have on disc nutrition and disc health. The goal of this study is to undertake a pilot study to determine the feasibility and preliminary outcomes of utilizing quantitative MRI in human patients to quantify changes in disc health and trans-endplate transport over the course of physical therapy.

To do so, patients with low back pain and concomitant disc degeneration, who have not had prior spinal surgery, will be recruited. Recruited patients will undergo MRI T2-mapping and post-contrast enhanced T1-mapping of their lumbar spines at 1.5T to measure disc health and nutrition, respectively. Patients will then begin a 6 week physical therapy treatment regimen, after which the same MRI scans will be performed again on each patient. Pain and disability level of patients will be assessed via the visual analog scale (VAS) and Oswestry Disability Index (ODI) questionnaires, both pre- and post-treatment. Lumbar active range of motion will also be quantified at the initial and final in-office physical therapy session. Inclinometers will be placed at the thoracolumbar junction and sacrum, and the patient asked to bend forward and backward. Lumbar flexion will be quantified as the difference in motion between the two inclinometers.

Significant differences T1 and T2 values in the disc, as well as VAS and ODI scores and lumbar range of motion, before and after physical therapy will be assessed via a paired t-test, with significance defined as p\<0.05. Univariate linear correlations between the changes in T1 or T2 values and changes in VAS, ODI scores and lumbar range of motion will be performed to determine if altered disc health or nutrition with physical therapy is significantly correlated with improvements in pain and disability.