What is it?
The facet joints are small stabilizing joints that are located in pairs between and behind each adjacent vertebrae at every level of the spine except at the uppermost two levels. They are weight bearing structures and are subject to mechanical stress.
Functioning with the vertebral body and intervertebral disc the facet joints allow you to bend and twist via a sliding motion of the two joint surfaces.
Facet joints have cartilage and are lubricated with synovial fluid that is kept within the joint by a capsule which surrounds the joint.
Synovial cysts are benign, fluid-filled sacs that develop in the facet joints. If large enough, these sacs can exert pressure on one or more nerve roots in the spinal canal or where a nerve exits the spinal canal.
What causes it?
Mechanical stress can lead to degeneration of the facet joint. With increasing degeneration synovial fluid can build up in an attempt to protect the joint. Once enough fluid forms under pressure then a contained synovial cyst can form.
There is increased risk of a cyst forming when there is increased stress and movement at that vertebral segment.
What are the signs and symptoms?
Typical symptoms will usually include one or more of the following: low back pain, buttock, hip, and leg pain.
The leg pain may occur in one or both legs, and usually radiates down the back more so than front of the leg towards the foot. There may be associated numbness and/or weakness.
How is it diagnosed?
The diagnosis of a synovial cyst begins with a complete history and physical exam. A synovial cyst is primarily diagnosed by an MRI where the cyst can be visualized and whether it compresses a nerve root or causes central stenosis. X-rays, including flexion/extension (i.e. bending) motion views, are important to rule out excessive movement (i.e. spinal instability) and to look for the presence of degenerative spondylolisthesis. Nerve irritation can occur from these changes. Electromyography (EMG) is occasionally performed to determine if there is evidence of nerve damage rather than just nerve root irritability.
What are the treatment options?
The first treatments should be non-invasive and include such methods as postural correction, activity alteration, improving muscle flexibility, strengthening and medications to reduce inflammation and nerve irritability. Commonly such treatments are performed by physical therapists and coordinated by your nonsurgical spine provider.
When these more conservative treatments fail then fluoroscopically guided interventions can be considered.
Facet joint injections involve placing anti-inflammatory corticosteroid agents into the joint to reduce joint inflammation, irritability and pain. Occasionally, the cyst can be aspirated through the joint or there is an attempt to rupture the cyst via a higher pressure facet injection.
Nerve root irritability and pain can be directly treated with a focused anti-inflammatory epidural steroid injection where the specific nerve root that is painful is targeted with corticosteroid. A combination of a facet joint cyst aspiration or rupture, with an epidural steroid injection, is commonly performed.
Post injection rehabilitation methods are often reinstituted in hopes of synergistic effects occurring from this combined care approach.
If all other options fail to provide pain relief then surgery is a consideration. The most common type of spine surgery for synovial cysts is a simple decompression performed by a minimally invasive technique. However, if there is instability associated with the joint then a decompression with fusion is more likely to be recommended to prevent further instability and recurrence of a cyst.