Prior to the injection, the facet joints have to be defined according to standard radiological techniques (e.g. MRI and physical correlation). Patients are then sent to 18F-Fluoride-PET/MRI imaging, in order to localize facet joints with increased uptake. Facet joints to be injected are again defined according to the location(s) of highest uptake as demonstrated by 18F-Fluoride-PET/MRI.

The defined injection sites before and after PET/MRI are compared. In equal defined injection sites, patients are sent for infiltration as scheduled, otherwise patients are randomized into two groups.

One group will undergo facet injection(s) according to the 18F-Fluoride-PET/MRI result, with standard injections performed under CT-guidance by the radiology department of the study site. The control group will undergo facet injections blinded to the 18F-Fluoride-PET/MRI results, but based on current standard clinical practise (MRI and clinical correlation).

The patients are asked to complete a validated pain and function questionnaire immediately before the facet joint injection, at 15 minutes, 1 day, 1 week and 1 month after the injection, as performed routinely in our institution.

The purpose of this study is to prospectively evaluate the value of 18F-Fluoride-PET/MRI imaging in patients with low back pain with evidence of painful facet joint arthropathy, which would potentially benefit from facet joint injections.

Inclusion Criteria:

1. Patients over 18 years old with low back pain who have failed conservative management in the primary care setting, namely, analgesia and physical therapy.
2. Imaging evidence (e.g. MRI) of facet joint degeneration, such as facet hypertrophy, subchondral sclerosis, and joint space narrowing.
3. Obtained informed consent

Exclusion Criteria:

1. had undergone prior spinal surgery or prior facet joint injections or
2. had other spinal abnormalities (benign or malignant tumors, congenital defects, isthmic spondylolisthesis) or
3. are unable to tolerate PET/MRI imaging
4. are pregnant or nursing.