Facet Joint Characteristics

Facet joints are synovial articulations that are enclosed in a capsule and supported by ligaments; they respond to trauma and arthritic changes similar to any peripheral joint.

Various types of meniscoid-like structures or invaginations of the facet capsules are present in the zygapophyseal joints of the spine. They are synovial reflections containing fat and blood vessels. In some cases, dense fibrous tissue develops as a result of mechanical stresses. Some people describe entrapment of these structures between the articulating surfaces with sudden or unusual movement as a source of pain and limited motion via tension on the well-innervated capsule. Bogduk and colleagues described the locked-back mechanism as being extrapment of the meniscoids in the supracapsular or infracapsular folds, which then blocks the return to extension from the flexed position. It is called an extrapment because the meniscoid fails to re-enter the joint cavity; consequently, it becomes a space-occupying lesion in the capsular folds, causing pain as it impacts against and stretches the capsules.

Common Diagnoses and Impairments from Facet Joint Pathologies

The etiology of facet joint pathologies may be trauma, degenerative, or systemic pathologies.

Facet Sprain/Joint Capsule Injury
There is usually a history of trauma, such as falling or a motor vehicle accident. The joints react with effusion (swelling), limited range of motion (ROM), and accompanying muscle guarding. The swelling may cause foraminal stenosis and neurological signs.

Osteoarthritis, Degenerative Joint Disease, Spondylosis
• Usually there is a history of faulty posture, prolonged immobilization after injury, severe trauma, repetitive trauma, or degenerative changes in the disk.
• During the early stages of degenerative changes, there is greater play, or hypermobility/instability, in the three-joint complex. Over time, stress from the altered mechanics leads to osteophyte formation with spurring and lipping along the joint margins and vertebral bodies. Progressive hypomobility with bony stenosis results.
• Usually, where there is hypomobility, compensatory hypermobility occurs in neighboring spinal segments.
• Pain may result from the stresses of excessive mobility or from stretch to hypomobile structures. Pain may also be a result of the encroachment of developing osteophytes against pain-sensitive tissue or of swelling and irritation because of excessive or abnormal mobility of the segments.
• The encroachment of osteophytes on the spinal canal and intervertebral foramina may cause neurological signs, especially with spinal extension and side bending.
• The degenerating joint is vulnerable to facet impingement, sprains, and inflammation, as is any arthritic joint.
• In some patients, movement relieves the symptoms; in others, movement irritates the joints, and painful symptoms increase.

Common Impairments and Functional Limitations Related to the Facet Joint Pathology

• Pain: When acute, there is pain and muscle guarding with all motions; pain when subacute and chronic is related to periods of immobility or excessive activity.
• Impaired mobility: Usually hypomobility and decreased joint play in affected joints; there may be hypermobility or instability during early stages.
• Impaired posture.
• Impaired spinal extension: Extension may cause or increase neurological symptoms due to foraminal stenosis; therefore, may be unable to sustain or perform repetitive extension activities without exacerbating symptoms.
• Any functional activity that requires flexibility or prolonged repetition of trunk motions, such as repetitive lifting and carrying of heavy objects, may exacerbate symptoms in the arthritic spine.

Rheumatoid Arthritis
• Symptoms of rheumatoid arthritis (RA) can affect any of the synovial joints of the spine and ribs. There is pain and swelling.
• RA in the cervical spine presents special problems. There are neurological symptoms wherever degenerative change or swelling impinges against neurological tissue. There is increased fragility of tissues affected by RA, such as osteoporosis with cyst formation, erosion of bone, and instabilities from ligamentous necrosis. Most common of the serious lesions are atlantoaxial subluxation and C-4/5 and C-5/6 vertebral dislocations.
• Pain or neurological signs originating in the spine may or may not be related to subluxation. Therefore, these signs should be used as a precaution whenever dealing with this disease because of the potential damage to the spinal cord.
• X-ray examinations are important in ruling out instabilities; signs and symptoms alone are not conclusive.

Facet Joint Impingement (Blocking, Fixation, Extrapment)
With a sudden or unusual movement, the meniscoid of a facet capsule may be extrapped, impinged, or stressed, which causes pain and muscle guarding. The onset is sudden and usually involves forward bending and rotation.
• There is loss of specific motions, and attempted movement induces pain. At rest, the individual has no pain.
• There are no true neurological signs, but there may be referred pain in the related dermatome.
• Over time, stress is placed on the contralateral joint and on the disk, leading to problems in these structures.

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