The articular facets are the small joints that connect the vertebral bodies of our spine. Many people know of the disc joint, but it is the articular facet that guides and directs the range of motion of one vertebra on another. The spacing between these two boney surfaces is very thin. Each joint surface also contains articular cartilage and a small meniscus tissue. Interestingly enough, these little guys are very important and when they begin to develop some wear and tear then they can really pack a punch. It is also important to know about the quality of soft tissue around the facet. For example, the each facet joint has a capsule, which has ligaments as well as small inter-segmental muscles that control and move each joint.
An injury to the soft tissue or inter-segmental muscle of the articular facet can be termed as primary or a secondary lesion and sometimes we call it, “dysfunction”. Meaning, that a primary dysfunction can be due to direct trauma or micro-trauma, either as a single insult or as a result of a series of micro-traumas directly to the facet itself such as with a repetitive poor computer posture. In that instance the facet joints get compressed by constantly pounding the articular surfaces together and thus the surrounding tissue gets inflamed. A secondary lesion or dysfunction is when a primary lesion causes the presence of some dysfunction elsewhere in the body. The facets potentially can cause a secondary lesion such as in legs and arms and that can manifest as changes in strength, coordination, endurance as well as peripheral soft tissues abnormalities and faulty neural elements. Secondary lesions have also been termed Somatic Dysfunction in the old osteopathic literature, which has now been classified as a type of referred pain. See the list below.
Interestingly enough, if a facet joint or joints are jammed, impacted or restricted at one or more sites then we might expect to find a palpable change in tissue quality, and we would term this a primary dysfunction. If a primary lesion goes uncorrected for several weeks or months, then it can actually cause secondary lesions to occur in the peripheral soft-tissue, usually in a predictable pattern. The formation of trigger points, muscle spasms and strength changes fall into this category. If the homeostatic mechanics are capable of restoration at that primary lesion then the secondary dysfunction, may spontaneously correct providing the secondary lesion has not been there for too long.
If secondary changes are not corrected once the primary lesion is restored, perhaps due to weakness, muscular imbalance, or habit, then the secondary lesion may become a self-maintaining entity of dysfunction in its own right. The secondary change then will need to be addressed independently from the primary facet lesion, but only after the facet restriction has been restored to normal mechanics.
As a tangible example, the hard bony prominences around the facet joint may indicate arthritic exostoses [An exostosis (plural: exostoses) is the formation of new bone on the surface of a exisisting bone]. These are common and are considered primary lesions in this discussion. When these bony prominences are not covered by soft spongy tissue, the therapist’s interpretation is that although they indicate osteoarthritic changes in the facet joint, the arthritic process is currently inactive and not a source of pain. However, when the tissue overlying the exostoses is thickened it can be considered a secondary lesion. The thickening varies between two extremes, from being like tough dry leather to being very soft and spongy. The more leathery it is the less likely is to be causing other than mild local symptoms, whereas the softer it is the more likely it is to be of recent origin and associated with recent symptoms. In the diagram here (from Maitland, 2002), the joint surface is the white solid area and the soft tissue changes around the facet are shown just off to the side but those would actually be surrounding the entire joint.
If you suspect you have a facet dysfunction, whether primary or secondary you should consult a knowledgeable physical therapist to evaluate your pathology and guide you on the proper treatment plan.