Facet joints are formed by the articulations of the superior and inferior articular processes of adjacent vertebrae. Except for the atlantooccipital and atlantoaxial joints, facet joints are lined with synovium and covered by a true joint capsule. The capsule is richly innervated. Each facet joint receives innervation from two spinal levels, one of which is from the dorsal ramus at the same vertebral level and the other of which is from one level above. This explains why facet-related pain is not easy to locate.
The spine can be considered as a series of connected motion segments. In each segment, the superior articular process of the lower vertebra connects the inferior articular process of the superior vertebra. Thus, the spine alignment and load distribution are thought to play an important role in the development of the degeneration of facet joints.
Instability of the spine due to trauma or poor posture that loads extra weight on the posterior structures of the spine may also cause degeneration of the facet joints.
The prevalence of facet arthritis is age-related. The study done by Manchikanti et al. reported a prevalence of facet joint involvement of 35% to 42% in patients with neck pain. In the lumbar area, the prevalence was 18% to 44% across age groups.
Degeneration changes in facet joints will involve the articular cartilage, synovium, and capsule. Thinning of the cartilage, formation of synovial cysts, fibrocartilage proliferation of the capsules, and osteophyte formation all can be seen in facet arthritis. Topographically, the prevalence of facet arthritis is the highest at L4-L5, followed by L5-S1. In cervical region, it is more common in the mid-cervical region, (between the C3 and C5 vertebrae).
The joint capsule starts to have fibrosis, neovascularization, and inflammation in the early stage of the disease. Later, extensive fibrocartilage proliferation contributes to the hypertrophied capsule. Osteophytes form at the later stage of the disease, usually at the border of the capsular insertion.
Painful conditions related to facet arthritis usually occur after sudden twisting or flexion/extension of the spine while lifting or after acceleration-deceleration injuries. Depending on the level of injury, the pain is usually localized over neck or back with some degree of radiation into the upper or lower limbs in a non-dermatomal distribution.
In the upper cervical spine, the referred pain tends to transfer up to the occipital region and may be combined with a headache. In the lower cervical spine, the referred pain tends to be down to the shoulder girdle and inter-scapular region. In the lumbar spine, the referred pain is around the buttock and thigh and rarely passes beyond the knee.
Pain related to facet arthritis, compared with radicular pain, is not likely to accompany with neurologic findings such as a motor or sensory loss or diminished reflexed.
Physical examination, including tenderness over the facet joint and pain aggravated by extension/rotation and relieved by flexion, are indicative of possible facet arthritis.
One clinical test that has been described to diagnose facet arthritis is the Kemp test. A patient will be asked to perform extension combined with the rotation of the spinal region of interest, with a positive test defined as a reproduction of the patient’s pain. However, the diagnostic accuracy is not high according to the systemic review performed by Kent et al.
The evaluation of pain-related facet arthritis should first be focused when ruling out conditions such as disc herniation, spinal stenosis, spondylolisthesis, infection, and neoplasm of the spine. The combination of facet arthritis with the above-described conditions is not rare. Thus, the role of conventional radiography, CT, and MRI on facet joint degeneration is not only to detect them but also to rule out other possible comorbidities.
CT scan, when detecting facet arthritis, is the most sensitive technique. MRI, on the other hand, can best detect the surrounding soft tissues such as a disc, spinal cord, neuroforamen, nerve roots, etc. Conventional radiography can help to detect motion-related instability in flexion or extension.
Some invasive techniques are used for evaluation as well. Facet block through intra-articular injection or medial branch block is useful in the diagnosis of painful conditions related to degenerative facet joints.
Physical therapy, pain medications, spinal manipulation, facet block, radiofrequency lesioning, and surgical intervention all can be used to treat pain related to facet degeneration.
Physical therapy includes education of proper posture and restoration of correct body mechanics. Positions such as excessive extension or extension with rotation should be avoided. Strengthening of deep neck flexors and abdominal muscles can help to balance the overactivated extensors of neck and back.
Pain medications such as steroids, nonsteroidal anti-inflammatory drugs(NSAID), or cyclo-oxygenase-2 inhibitor(COX-2) can be given orally for initial pharmacologic treatment of acute pain related to facet arthritis or following acute exacerbation of chronic pain related to facet arthritis.
Spinal manipulation, by using the muscle energy technique or high-velocity low-amplitude maneuver to correct the type II dysfunction of the facet joints (flexion-rotation-side bended or extension-rotation-side bended postures) can help to realign the facet joints and can alleviate pain.
Landmark-guided, ultrasound-guided or fluoroscopically guided techniques in facet block or medial branch block can be used to treat pain related to facet arthritis. Radiofrequency lesioning of the medial branch of the posterior ramus can be used if the pain is recalcitrant to the previous block.
Surgical intervention is not the first-line treatment for the management of facet arthritis. Surgery is indicated when there is a combination of other diseases such as severe spinal stenosis or herniated discs that produce intractable pain, loss of motor function, or incontinence.
Facet arthritis may be manifested like other musculoskeletal disorders. Examples differential diagnoses include:
Laxmaiah et al. conducted a randomized control study and revealed that medial branch blocks with local anesthetic and Sarapin, with or without steroids, can bring significant relief to pain related to facet arthritis. The relief with one to three injections was 100% up to one to three months, 82% for four to six months, 21% for seven to 12 months, and 10% after 12 months.
The first step to treat facet arthritis is patient education of proper posture during daily living, relative rest, pain relief, and exercise. After physical therapy, if the pain persists, facet blocks can be done to help further understand if the pain is really from the facet joint itself, which helps the practitioner arrange further treatment if needed.