Facet joints are symmetrical synovial joints with fibrous capsules that connect the articular facets of the vertebrae. The superior articular process of the lower vertebra articulates with the inferior articular process of the upper vertebra. Facet joints are located between the lamina and pedicle of the same vertebra and form the articular pillars for stability of the vertebral column [1].

There are three common weight-bearing units: one anterior-located intervertebral disc (or vertebral body) and two posterior-located facet joints. If the anterior weight-bearing unit is disrupted or fails, the facet joints will suffer from excessive weight-bearing. For example, in the L3-L4 intervertebral disc level, 80% of weight-bearing is distributed to 90% of the surface-area of the intervertebral disc and 20% of weight-bearing is allocated to 10% of the surface-area of both facet joints [2]. This means that each facet joint, compared to the intervertebral disc, has twice the weight-bearing burden per surface area under normal conditions. However, if there is a compression fracture of the vertebral body or a herniated nucleus pulposus occurs to develop anatomical disruption or functional failure to support the anterior weight-bearing, the posterior facet joints will bear more weight than nit can sustain, provoking degenerative facet joint disorders and their related pain.

One of the most common sources of spinal pain syndromes is the facet joints. Cervical, thoracic, and lumbar facet joint pain syndromes comprise 55%, 42%, and 31% of chronic spinal pain syndromes, respectively [3].

Common facet joint disorders are degenerative disorders, such as osteoarthritis (OA), hypertrophied superior articular process (HSAP), and facet joint cyst (FJC); infection, such as septic arthritis; systemic and metabolic disorders, such as ankylosing spondylitis or gout; and traumatic dislocations [4].

Pain from facet joint disorders may show double-faced characteristics. Facet joint pain from OA is described as representative referred pain from the deep somatic structure, similar to the visceral structures. However, if degeneration of the facet joint progresses, HSAP or FJC compresses the dorsal root ganglion (DRG), eliciting radicular pain (a kind of radiating pain). Thus, patients with facet joint disorders causing both referred and radicular pain are not able to indicate the actual focus of pain.

This review introduces the diagnosis and treatment of various painful facet joint disorders including degeneration, infection, and trauma.

1. Degenerative facet joint disorders

1) OA of the facet joints and facet joint syndromes

The most common facet joint disorder is OA. Facet joint degeneration may develop from as young as 15 years old. Almost 2/3 of people show some degree of degeneration before they are 30 years old and everyone does before they are 60 years old [1,5].

The most frequently affected facet joint is L4-L5, followed by L3-L4 and L5-S1. OA is more frequent in high body mass index. However, it is not different between male and female patients [5]. Morphological changes seen in imaging diagnosis for OA include ① joint space narrowing, irregularity, or vacuum phenomenon, ② osteophytosis or hypertrophy of the articular processes, and ③ subchondral erosions, cysts, or sclerosis [5,6].

There are various grading systems for OA based on the above morphological changes using plain film, computed tomography, and magnetic resonance imaging. Kellgren and Lawrence [7], who are well-known for grading knee OA, described the degree of the OA affecting various diarthrodial joints, including the cervical and lumbar facet joints in 1957. They divided OA of the facet joint into 5 grades on lateral plain films: none (grade 0), doubtful (grade 1), minimal (grade 2), moderate (grade 3), and severe (grade 4). Radiologic features include narrowing of the joint space associated with subchondral sclerosis or cysts and osteophytes of the articular processes.

Pathria et al. [8] classified lumbar facet joint degeneration into 4 grades from oblique radiography and computed tomography: grade 0 (normal), grade 1 (mild: joint space narrowing), grade 2 (moderate: joint space narrowing with subchondral sclerosis or articular process hypertrophy), and grade 3 (severe: joint space narrowing with subchondral sclerosis and articular process osteophytes).

Facet joint pain syndrome is suspected from an analysis of history (referred pain pattern) and physical examination (tenderness). It is confirmed by two consecutive diagnostic injections into the medial branch of the posterior ramus or direct facet joint injection. The treatment includes the same as the diagnostic procedures, such as a medial branch block or facet joint injection.

However, the medial branch block has some limitations for use as a diagnostic and therapeutic tool. The medial branch innervates not only the facet joints, but also the skin, subcutaneous tissue, erector muscles, spinous process, lamina, and ligaments. Therefore, it is difficult to determine the facet joints as the source of the spinal pain, in the case of pain relief from medial branch block. In addition, the painful facet joints produce some inflammatory substances, such as substance P, interleukin-6, and tumor necrosis factor-alpha [9–11].

Hence, it is essential for relieving facet joint pain to inject anti-inflammatory agents directly into the facet joints. For patients who will receive a total knee replacement, a medial branch block, rather than facet joint injection, seems to be a similar situation in the operating room by performing a therapeutic block and letting the patients return to the ward without surgery after pain relief. In conclusion, a medial branch block is not considered to be effective for the diagnosis and treatment of facet joint pain.

Bogduk [12] recommended medial branch blocks rather than facet joint injections in the cervical spine for the following reasons. The medial branch block has merits: ① It is easy to perform and less traumatic due to its superficial location, and ② it has less risk for penetration of the vertebral artery. On the other hand, ③ facet joint injections need a skillful technique for an obliterated facet joint, and ④ no study had been performed showing the benefits of facet joint injections. However, the facet joints are fully opened in the anteroposterior fluoroscopic view if a patient can flex his or her neck in a prone position. There is no risk if the needle is located within the targeted facet joint. And, currently, sufficient studies have accumulated showing the benefits of facet joint injections.

Imaging studies, such as increased uptake on the radionuclide bone scan, computed tomography, and magnetic resonance imaging on T1 images after gadolinium injection, cannot determine the exact painful structures. Referred pain from facet joints, a kind of representative deep somatic pain, always confuses non-pain specialists to perform various differential diagnostic examinations. In cervical facet joint pain syndrome, patients commonly complain of shoulder pain around the scapulae. Patients with thoracic facet joint pain frequently complain of flank pain. In patients with lumbar facet joint pain, the buttock or thigh becomes a common region where they complain of pain.

HSAP or FJC may provoke radicular pain that compresses the DRG. Basically, the DRG is located in the foraminal zone; these facet lesions originate from the subarticular zone, outside of the central zone and inside of the foraminal zone. If the facet lesions compress the spinal cord, they produce central spinal stenosis; if these lesions grow enough to compress the DRG, they produce foraminal stenosis, provoking radicular pain. Provocation of radicular pain from thorough physical examination of a positive straight leg raising or Lasègue test suggests the lesions compressing the DRG, and further evaluation for imaging diagnosis is needed [13].

(1) Cervical facet joint syndrome

Dwyer et al. [14] investigated the cervical facet joint pain patterns from 5 normal volunteers. They injected contrast medium into the facet joints at the segments C2-C3 to C6-C7 under the fluoroscope. Aprill et al. [15], in conjunction with the above authors, also compared the referred pain pattern to 10 patients with suspected cervical facet joint pain, and 9 patients showed a good match for pain location using fluoroscope. Dreyfuss et al. [16] performed provocative injections into the atlanto-occipital and atlanto-axial joint to reveal pain referral zones. In addition, Fukui et al. [17] investigated the distribution of the referred pain pattern from the cervical facet joints from C0-C1 to C7-T1 and the cervical dorsal rami from the C3 to C7 in 61 symptomatic patients. Thanks to their investigation of cervical facet joint pain patterns, heavy, dull, and obscure neck, upper back, and shoulder pain may originate from the joints (Fig. 1A).

Figure 1. Referred pain pattern from the facet joints. (A) Cervical facet joint syndrome. It is quite difficult to differentiate referral patterns to the greater occipital protuberance from the atlanto-occipital joints and atlanto-axial joints. One of the most common referral pain patterns to the supraspinatus and infraspinatus area with interscapular area originates from the C5-C6 and C6-C7 facet joints, respectively. These facet joints become the common targets of neck straightening. (B) Thoracic facet joint syndrome. Mid-back pain with referred pain to the chest and abdomen arises from senile kyphosis, a long-term sleeping with a semi-Fowler position with the head of the bed at 30°–45° due to respiratory difficulty or intractable abdominal pain, or osteoporotic or osteolytic compression vertebral fractures. (C) Lumbar facet joint syndrome. Referral pain patterns from the upper and lower lumbar facet joints are shown to the groins and buttocks, respectively. It occurs commonly after fusion surgery as junctional pain syndrome.

The cervical lordotic curvature is visible at 10 weeks of fetal development due to the posterior wedging when the anterior column of the vertebral bodies and intervertebral discs become greater than the posterior column of facet joints [18]. This lordosis is very helpful for mastication, breathing, vocalization, eye movement with staring, and shock absorption. The lordotic configuration can resist large compressive loads and also reduces stress on the vertebral endplates. Thus, the compressive load is distributed onto the anterior column and posterior column, 36% and 64%, respectively; this is one of the reasons why facet joint disorders are the most frequent in the cervical region [18].

The most common and reliable measurement for the cervical lordosis is Cobb’s angle, between the lower endplate of the C2 and C7 body in the lateral radiographic view. The angle is obtained from the angle of the intersection of the perpendicular lines which are drawn from the previous two parallel lines. The normal Cobb angle between the C2 and C7 is considered to be 23° (20°–35°) [19].

Cervical facet joint injections are frequently performed in patients with neck straightening and myofascial pain syndrome, confirmed diagnosis of lesions of the anterior column, such as herniated nucleus pulposus, spinal stenosis, or osteolytic compression fracture in imaging studies, and those with a history of whiplash-associated disorders (WADs) [20].

In the clinical field, straightening of the cervical curvature is easily recognized by the loss of the prominent and palpable C7 spinous process. Patients with cervical facet joint pain complain of neck and shoulder referred pain. The most common affected facet joints are C5-C6 and C6-C7, and referred pain is distributed into the supraspinous area and infraspinous/interscapular area, respectively. Even though pain referral regions from the C5-C6 and C6-C7 facet joints seem to be similar to those of upper thoracic facet joints, they do not distribute to the flank. It is quite difficult to palpate the C1 to C4 facet joints separately because the levator scapulae muscle originates so closely from the posterior tubercles of the transverse processes. In addition, the lower, rather than upper, cervical facet joints are also difficult to palpate due to muscles. Unlike the thoracic and lumbar facet joints, referral pain pattern and Cobb angle rather than tenderness on the facetal area is helpful in suggesting cervical facet joint pain.

A proper interventional procedure does not secure permanent pain relief unless the patients try to maintain the gravity line [from the external auditory canal, dens of the axis (occipito-atlanto-axial junction), cervico-thoracic junction, thoraco-lumbar junction, lumbo-sacral junction, hip joint, knee joint, and ankle joint in the lateral view] [21]. Therefore, it is essential to encourage them to do self-directed exercise to maintain the gravity line to prevent recurrence [22]. In addition, botulinum toxin injections into the trapezius, levator scapulae, sternocleidomastoid, and masseter muscles in cases of long-standing myofascial pain syndrome may also be helpful to alleviate pain after the removal of cervical facet joint pain.

At least one medial branch is found at each dissected cervical level. The medial branch originates from the dorsal ramus immediately after becoming the spinal nerve, and follows the pedicle toward the respective target muscles, such as the multifidus and semispinalis cervicis muscles. The direct facet joint branch did not innervate muscles as its name. In addition, facet joint innervating branches were 1 or 2 [23].

Generally, a cervical facet joint receives a medial branch of the dorsal ramus from the spinal nerve above the facet and the nerve below. For example, the C4-C5 facet joint receives the medial branches of the dorsal rami of the C4 and C5 spinal nerves.

It is recommended to perform cervical facet joint injections with flexion of the neck to open the joint widely in a prone position under the anteroposterior fluoroscopic view. Self-directed exercise for stretching for the trapezius and levator scapulae muscles of the posterior neck and temporalis, masseter, and sternocleidomastoid muscle of the anterior neck is required [20,22].

(2) Thoracic facet joint syndrome

It is common to find thoracic facet joint syndrome followed by a long-standing straightening of the cervical spine. Patients with thoracic facet joint pain frequently visit cardiology department due to referred pain to the flank and anterior chest. It is also easy to find inpatients with long-standing intractable abdominal pain or respiratory difficulty, caused by sleeping in a semi-Fowler’s position.

Dreyfuss et al. [24] underwent provocative intraarticular injections into thoracic facet joints from T3-T4 to T10-T11. Significant overlap sharing 3–5 different joint referral zones occurred (Fig. 1B). Pain patterns from thoracic facet joints should be differentiated from those of the costotransverse joints. The costotransverse joint pain is a deep, dull aching, and pressure-like sensation, which is restricted to only the joints, not referred to the chest, upper extremities, as well as a pseudo-visceral pain, as in facet joint pain [25].

Thoracic hyperkyphosis is defined as a kyphosis angle greater than 40° in the thoracic spine which is the 95th percentile of normal for young adults. Women are two times more likely than men in older adults. As the kyphotic angle increases, physical performance or quality of life decreases. It is measured by T4-T12 Cobb’s angle in the standing lateral spine radiography. The angle is composed of two perpendicular lines which are drawn from the upper endplate of the T4 vertebral body and the lower endplate of the T12. The Debrunner kyphometer, in a standing position, is also used for measurement of kyphosis between the T2- T3 and T11-T12 interspace of the spinous processes. Lastly, a flexicurve ruler, made of a plastic, moldable device, is used for measuring a kyphotic index that is calculated as the width divided by the length of the thoracic curve, multiplied by 100. The ruler is aligned over the C7 spinous process to the L5-S1 interspace between spinous processes [26].

In cases of thoracic osteoporotic or osteolytic compression fractures, the most frequent regions of the spine, thoracic facet joint injections prior to percutaneous vertebroplasty have great merits: ① It is helpful to determine the necessity of percutaneous vertebroplasty or painful vertebral levels at that time which vertebroplasties are needed after the removal of facet joint pain; ② Patients can cooperate by lying in a prone position without facet joint pain during the vertebroplasty; and ③ Patients can get complete pain relief and sufficient satisfaction after vertebroplasty without facet joint pain [27].

In patients with recurrent thoracic facet joint pain, thermal radiofrequency ablation can be applied to the medial branches of the posterior rami. However, it is difficult to make a thermal lesion into the full-thickness of the medial branch even though the direction of the radiofrequency needle is parallel to the medial branch. It is better to perform alcohol ablation (painless over an average of 24 months) rather than repeated thermal ablation (painless for an average of 10.7 months) in recurrent cases after thermal radiofrequency ablation in thoracolumbar facet joint syndrome [28]. It is also helpful to administer a minimal dose of an anticonvulsant for positive neuropathic pain and an antidepressant for negative neuropathic pain, originating from the medial branches of the posterior rami for a short time, even after removal of somatic inflammatory pain using facet joint steroid injections. Tapering these medications is usually performed from thrice through twice to once in a day within one or two months.

The inner upper pedicle, from 9 to 12 o’clock on the right side and from 12 to 3 o’clock on the left side, in the anterior-posterior fluoroscopic view, commonly becomes the target of the thoracic facet joint injection. After feeling the sensation of the needle being inserted into the joint in the anteroposterior fluoroscopic view, confirmation of the insertion into the facet joint is used by contrast medium in the lateral fluoroscopic view [27].

(3) Lumbar facet joint syndrome

Fukui et al. [29] discovered the referred pain patterns from the lumbar facet joints and dorsal rami. They divided the pain distribution into 6 regions: the lumbar spinal region; gluteal region; trochanteric region; lateral thigh region; posterior thigh region; and groin region. The L1-L2 facet joint pain was only distributed into the lumbar spinal region. The L2-L3 facet joint pain was always distributed into the lumbar spinal region and was also rarely referred to the trochanteric, gluteal, and lateral thigh regions. The L3-L4 facet joint pain was distributed into the lumbar spinal region, and was referred to the gluteal, lateral thigh, posterior thigh, trochanteric, and groin regions, in order of frequency. The L4-L5 facet joint pain was distributed into the lumbar spinal region, and was referred to the gluteal, lateral thigh, trochanteric, posterior thigh, and groin regions, in order of frequency. The L5-S1 facet joint pain was distributed into the lumbar spinal region, and was referred to the gluteal, lateral thigh, posterior thigh, trochanteric, and groin regions, in order of frequency (Fig. 1C).

In addition, the L1 medial branch stimulation was distributed mainly to the lumbar spinal segment and rarely to the gluteal region. The L2 medial branch stimulation was distributed mainly to the lumbar spinal segment and rarely to the gluteal, trochanteric, groin, and lateral thigh regions. The L3 medial branch stimulation was distributed mainly to the lumbar spinal segment and rarely to the gluteal, trochanteric, groin, and lateral thigh regions. The L4 medial branch stimulation was distributed mainly to the lumbar spinal segment and rarely to the gluteal, trochanteric, lateral thigh regions, and posterior thigh. The L5 medial branch stimulation was distributed mainly to the gluteal and lumbar segment region and rarely to the posterior thigh, lateral thigh, and trochanteric regions [30].

Instrumentation or fusion is commonly performed in the lumbar spine; therefore, junctional facet joint pain is also frequently found in the lumbar spine. Junctional spinal disorders can be divided into simple segmental degeneration above or below instrumentation with or without spinal stenosis with ① proximal junctional kyphosis, ② distal junctional kyphosis, ③ intercalary junctional kyphosis between two instrumented segments of the spine, and ④ junctional scoliosis [30]. Proximal, distal, and intercalary junctional kyphosis forces the bilateral adjacent facet joints to bear a burden. However, junctional scoliosis usually produces a unilateral facet joint problem.

2) HSAP

HSAP is a common degenerative spinal disorder. As the disc space become shorter along with degenerative change, the SAP is worn out with osteophytes [31]. The facet joint is located in the subarticular zone among the four zones, adjacent to the central and foraminal zone. Therefore, an HSAP which compresses the spinal cord or DRG may provoke central or foraminal stenosis according to its shape and size. High SAP cross-sectional area values over 110.71 mm₂ were associated with lumbar central canal spinal stenosis [32]. Patients with lumbar foraminal stenosis revealed more sagittal facet joint orientation, more facet joint tropism, a larger SAP cross-sectional area, and smaller facet joint area [33]. HSAP commonly occurs at the mid-level of the cervical spine unilaterally, and it develops more frequently in men [34].

HSAP may present radicular pain instead of referred pain from typical OA of the facet joints. If straight leg raising test on physical examination shows a positive result, further corresponding imaging diagnosis is necessary. If HSAP is considered as a main source of radicular pain, interventional treatment is required.

Resection of the HSAP is usually performed for the decompression for a compressed exiting nerve root using a spinal endoscope. The resection should be restricted to the HSAP (less than 1/4 of the SAP), not involving the facet joint in order to prevent biomechanical deterioration. Resection of the HSAP can be performed using round and diamond shaped drill bits or manually with an annulotome [35].

3) FJC

The FJC is quite similar to other degenerative diarthrodial joints. The opportunity to detect asymptomatic FJC is increasing due to the development of magnetic resonance imaging. Half of FJC cases do not provoke pain; large anterior cysts cause radicular pain [36].

An FJC can compress the spinal cord, DRG, or nerve root, provoking central or foraminal stenosis. The capsule of the facet joint consists of a dense collagenous outer layer and an elastic inner layer, similar to the composition of the ligament flavum. The L4-L5 facet joint is the most frequent site of FJC in the lumbar spine because it displays the greatest amount of anteroposterior translation, followed by L5-S1 or L3-L4 and the L2-L3 level. It is more frequent in female patients in their mid-sixties. FJCs are usually associated with degenerative spondylolisthesis and adjacent disc and facet joint degeneration [37,38].

Heterogeneous composition, such as mucoid, serous, or hemorrhagic content, of FJCs is found with the different linings such as synovial, ganglion, or flavum cysts. The communicating canal is found between the facet joint and FJC; however, debris occludes the canal in 1/4 of cases. Synovial cysts are a herniation of the synovial membrane of the joint capsule filled with synovial fluid with/without communication with the joint; ganglion cysts are a lining with a collagenous capsule that surrounds a gelatinous liquid, rich in mucopolysaccharides [4]. Common symptoms of lumbar FJC include radiculopathy (sensory, motor, and reflex, in order of frequency), lower back pain, and neurogenic claudication, in descending order [37,38].

Interventional treatment for symptomatic FJC begins with a direct aspiration under the computed tomogram or fluoroscope-guided facet joint injection followed by bursting of the FJC confirmed by contrast medium. However, recurrence of cysts commonly occurs within 1 year because of the residual synovium, cystic type, and osmotic load of the contrast medium [36]. Therefore, the next step is endoscopic enucleation for the removal of the residual synovium using bipolar radiofrequency. The final minimally invasive procedure before fusion surgery is a facetectomy, removing less than 1/4 to prevent instability. Half of patients who had received intraarticular injection for bursting an FJC had recurrence within 3 years; half of patients who had received endoscopic enucleation also had recurrence within 3 years; No patients who had received facetectomy had recurrence within 3 years (Fig. 2) [39].

Figure 2. Three staged minimally invasive interventional procedures for the facet joint cysts. (A) The first step is placement of a needle into the targeted facet joint and injection of the contrast medium for bursting the facet joint cyst. However, half of ruptured cysts can grow again and elicit radiculopathy within 3 years. (B) Enucleation of the root of the cyst with using a bipolar radiofrequency after injection of mixture of contrast medium and indigo carmine into the targeted facet joint is the second step after bursting. However, half of the cases of cystic enucleation have recurrence. (C) Endoscopic removal of involved superior articular process after recurrence of cystic enucleation is the third step before open surgery with fusion for preventing recurrence of facet joint cyst. The hypertrophied superior articular process which compresses dorsal root ganglion is removed. Adapted from the article of Kim et al. (Pain Physician 2019; 22: E451-6) [39].

2. Septic arthritis of the facet joint

It is quite difficult to find facet joint infection alone without other spinal infections. Most spinal infections include spondylodiscitis with psoas abscess, epidural abscess, or facet joint infection, in order of frequency [40]. Hematogenous pyogenic facet joint infection occurs only in 4% of cases (6/140 cases) [41]. The most common level of the spine is lumbar, followed by the cervical and thoracic facet joints [42,43]. Common symptoms include not only febrile sensation but also back pain, radicular pain, and asthenia [44].

Diagnosis is performed by increased uptake on the radionuclide bone scan for early detection, computed tomography for facet joint lesion, and magnetic resonance imaging on T1 images after gadolinium injection for the spread of infection to the adjacent structures [45].

There are 4 different approaches for the treatment of spondylodiscitis, psoas abscess, epidural abscess, and facet joint infection using a spinal endoscope and epiduroscope [39]. Basically, spinal infections are treated with medical treatment after confirmation of the causative agent [46]. According to the sites of combined infection (commonly spondylodiscitis, epidural abscess with septic arthritis of the facet joint), spinal endoscopic and/or epiduroscopic debridement and irrigation, followed by biopsy to discover the causative agent, is a minimally invasive procedure in debilitated and septic patients under safe sedation using dexmedetomidine [47].

3. Trauma

Whiplash injuries can be caused by any events that result in hyperextension and flexion of the cervical spine [48]. The most common mechanism of a whiplash injury in over half of cases is rear-end collision; other similar events also cause WAD [49]. Therefore, WAD is defined as a cervical spinal injury secondary to an acceleration-deceleration mechanism, presenting neck pain, headache, dizziness, temporomandibular joint dysfunction, and secondary disturbance [50].

In rear-end collisions, 15% of patients experienced pain. Patients who had visited emergency departments complained of pain immediately (37%), within 12 hours (62%–65%), and within 24 hours (90%). One-third of patients complained of pain within 2 days while 2/3 of patients had pain from 3 to 69 days after the accident. The most common symptoms were neck pain and stiffness, occipital headache, thoracolumbar back pain, and paresthesia of the upper limbs. In addition, subacromial impingement and irritation of the brachial plexus were also found. Patients were free from symptoms after 2 and 3 months, with a proportion of 88% and 93%, respectively [49].

Two commonly used classifications based on symptom severity are the Quebec Classification and the Gargan and Bannister Grading System (Table 1) [51,52]. The facet joint has been identified as the most common pain generator in 50% (27%–70%) of cases [49,52]. Mechanical hyperalgesia caused by painful facet joint distraction is associated with spinal neuronal hyperexcitability. Neuronal metabotropic glutamate receptor-5 and protein kinase C-epsilon with glutamate transporter (excitatory amino acid carrier 1) in WAD, were observed in the DRG and spinal cord on days 1 and 7, respectively [53]. The most common painful levels of the cervical facet joints are considered to be C5-C6 and C2-C3; the most frequently affected sites radiologically are C2-C3, C3-C4, and C5-C6 [52].

Table 1 Comparison between Classification of Whiplash Associated Disorder by the Quebec Classification and the Gargan and Bannister Grading System [51,52]

Grade	Quebec Classification	Grade	Gargan and Bannister Grading System
0	No symptom	A	No symptom
1	Complaint of neck pain, stiffness, or tenderness only without physical signs	B	Nuisance symptoms with no interference with leisure or activity
2	Neck complaint and musculoskeletal signs, including decreased range of motion and point tenderness	C	Intrusive symptoms requiring analgesics, orthotics, and physical therapy
3	Neck complaint and neurological signs, including decreased or absence of tendon reflex, weakness, and sensory deficits	D	Disabling symptoms requiring time off work, regular analgesia, orthotics, and repeated medical consultation
4	Neck complaint and fracture or dislocation

Facet joint disorders, including degenerative disorders, infections, and trauma, are very common in spinal pain disorders; however, they are not easy to diagnose due to having referred or radicular pain from the same structure. The degree of degeneration of the facet joint does not always match severity of pain.

Cervical facet joint disorders should be differentiated from shoulder girdle and intervertebral disc disorders; lumbar facet joint disorders are also differentiated from pelvic girdle disorders, intervertebral disc disorders, and disorders from the lower extremities. To have a glance at the gravity line of the patient is the best way to suspect facet joint disorders. Medial branch block cannot be a good diagnostic and therapeutic method for facet joint pain syndrome.

Treatments for degenerative facet joint disorders range from simple facet injections for referred pain in OA to decompression for mass effect in FJC or HSAP. Septic arthritis of the facet joint can be treated by minimally invasive spinal surgery using the spine endoscope and systemic antibiotic mediation.

This study was supported by a research grant from Pusan National University Yangsan Hospital in 2023.

Data sharing is not applicable to this article as no datasets were generated or analyzed for this paper.

Kyung-Hoon Kim is an editorial board member of the Korean Journal of Pain; however, he has not been involved in the peer reviewer selection, evaluation, or decision process of this article. No other potential conflict of interest relevant to this article was reported.

Yeong-Min Yoo: Writing/manuscript preparation; Kyung-Hoon Kim: Writing/manuscript preparation.

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