The literature describes the presence of intra-articular structures in the zygapophyseal (facet) joint (Bogduk & Engel 1984, Bogduk 1997). The largest of these structures is attached via synovium to the inner surface of the superior and inferior capsules. They project up to 5 mm into the joint space. The apex of these structures is wedge-shaped and consists of densely packed collagen. Their functional significance is thought to be two-fold (Bogduk & Engel 1984, Bogduk 1997):
I. to act as a passive space filler to provide greater stability;
II. to protect the joint surfaces when they become unopposed during normal flexion and extension movements.
Giles and Taylor (1987) have reported that the capsule and synovial folds of the facet joint of the lumbar spine are richly innervated. In fact, the facet joints receive their nerve supply from the medial branch of the dorsal rami (Bogduk 1997).
Various authors (Mooney & Robertson 1976, Bogduk 1997) have shown that facet joint pain referral patterns occur predominantly in the buttock and thigh. However, symptoms can extend into the distal part of the lower limb (McCall et al. 1979). Mooney and Robertson (1976) demonstrated that injecting an irritant into the facet joints could diminish straight leg raise (SLR) and deep tendon reflexes.
Studies have used the response of pain relief to facet joint injection as indicative of facet joint pain (Schwarzer et al. 1994a, b, 1995). The incidence of the facet joint causing low back pain is considered to be low compared to the disc (Kuslick et al. 1991, Schwarzer et al. 1994a, Bogduk 1997). In two studies, the proportion of cases with lumbar zygapophyseal joint pain varied from 15% in injured workers (Schwarzer et al. 1994a) to 40% in elderly patients (Schwarzer et al. 1995). Concurrent facet joint pain and discal pain were found to be rare (Schwarzer et al. 1994b). However, there is a great deal of controversy about the ability of clinicians to differ- entially diagnose facet and discal pathology, with most literature refuting the reliability of any clinical tests (Dreyer & Dreyfuss 1996, Revel et al. 1998).
An ‘acute locked back’ is characterized by the sudden onset of pain on attempting extension from a bent position. An upright stance cannot be achieved and there is resultant antalgic muscle spasm. The patient may present with a shift and traditionally the joint is manipulated (Bogduk & Jull 1985).
A spinal treatment developed by Mulligan (1999) involves the application of a sustained mobilization along the facet treatment plane while the patient actively performs the painful physiological move- ment. These techniques are called sustained natural apophyseal glides (SNAGs). They are applied in a cephalad direction either centrally to the spinous process or unilaterally to the transverse process or articular pillar of the vertebra.
The following case study will outline an effective method of reducing an ‘acute locked back’ when the facet joint is implicated.