The long term goal of this project is dual fold. First, the investigators wish to derive, validate and then test the impact of a clinical prediction rule to determine which patients who suffer from CLBP with degenerative changes of the lumbar spine and referred pain to the legs are likely to require surgery and have successful outcomes in the long term. Second, the investigators would like to establish robust methodology and statistical analysis guidelines for creating clinical prediction rules in physical therapy research. This observational cohort project is a first step towards those goals. Here the investigators specifically aim to identify personal, behavioral, psychological, morphological, and physical factors that can predict the need for surgery as well as level of participation restriction in patients who suffer from CLBP with degenerative conditions of the lumbar spine and referred pain to the legs. The investigators will also explore which parameters can predict success after 1 month, 6 and 12 months in patients who underwent decompression/fusion surgery.

A classification-based approach to identify specific characteristics of patients who seriously suffer from chronic low back pain (CLBP) with referred pain to the legs who are likely to respond to certain interventions has become a research priority in the medical milieu in general and in physical therapy in particularly.While several classifications have been developed to predict success following physical therapy interventions, some have methodological flaws and no clinical prediction rules have been created for patients with CLBP with degenerative changes of the lumbar spine and referred pain to the legs who are likely to require surgery and have successful outcome post-surgery. CLBP is multifactorial and morphological findings such as degenerative changes of the lumbar spine may not explain the phenomenon in full. The international classification of functioning, disability and health allows for a comprehensive description of the patient as a whole and can be used to classify patients according to their anatomy, pathology, impairments and capacity One-hundred and fifty patients who suffer from CLBP with degenerative conditions of the lumbar spine and referred pain to the legs and are candidates for lumbar decompression/fusion surgery will be recruited from a physician office at the Meir medical center, department of orthopaedic surgery, "Kfar-Saba", Israel. The structure and pathology of their lumbar spine will be analyzed in detail from CT and MRI imaging (morphological measurements of their vertebra and the intervertebral discs). Another one-hundred and fifty CT and MRI imaging of non symptomatic low back group will be taken from the "Meir medical center" in order to characterize the symptomatic group and their degenerative changes.

Inclusion Criteria:

• Participants' diagnosis may include unstable degenerative spondylolisthesis, radicular pain, or documented stenosis with referred pain

Exclusion Criteria:

• Psychiatric illness
• Previous spine surgery
• Painful arthritic hip
• Hospitalization or surgery in the previous 6 months
• Alcohol consumption > 10 drinks/week
• Diabetes or other causes for poly neuropathy
• Metabolic bone disease, tumor, spinal deformity or contraindications to MRI

Participants with CLBP (>12 weeks) and degenerative changes of the lumbar spine confirmed by CT imaging who were recommended surgery and chose to undergo surgery will be recruited from the department of Orthopedic Surgery at the Meir Medical Center, Kfar-Saba, and in Assuta hospital, Tel Aviv, Israel. Included participants will be men or women, aged 40-80 years, of any race or ethnic background. Participants' diagnosis may include unstable degenerative spondylolisthesis, radicular pain, or documented stenosis with referred pain