Low Back Pain – Facet vs Disc
Two of the most common causes of low back pain presenting in clinic are discogenic (disc) or facet joint related pain. Injury to either can cause severe discomfort, limiting a person’s movement and ability to carry out normal daily activities. The facet articulations are small joints along each segment at the back of the spine, controlling the movement of the spine. There are two of these joints at each vertebral level. The intervertebral discs are the primary shock absorbers, generally between a quarter and a half inch in height, interconnecting the bodies of the vertebral segments. Therefore, it can be considered that the discs and the facets create joint complexes that allow for both shock absorption and movement at each segment of the spine.
One of the primary symptoms with lumbar facet joint locking is an increase in pain on extension of the lower back, that is basically more pain when you try and straighten up your lower back or lean back on it. This position loads pressure on the locked, and now most likely inflamed lumbar facet joints. Usually in this type of injury there is pain relief to a certain extent when a person bends forward. The reason for this is that forward flexion decompresses the facet joint articulations, releasing some of the pressure on the joints and hence the associated pain. There can be nerve irritation with this injury but it is usually more general and not as severe as with discogenic pain.
When we start talking about disc injury, we are usually referring to a small tear in the outer annular fibers of a disc that has either resulted in a bulge, a protrusion, or an extrusion of the disc particle(see diagram). Pain occurs when a disc touches off a nerve due to one of these injuries, triggering a series of reactions, some of which include muscle spasm, inflammation and pain. Often the nerve root irritation sends pain signals down either the front or back of the leg depending on which disc level is affected. In contrast to facet joint injuries, with disc injuries, bending forward causes a significant increase in pain, as it usually increases compression of the disc against the nerve. So again to generalize, disc injuries are usually more sensitive to forward flexion, whereby facet injuries are very sensitive to backward extension. A classic and very telling sign of a disc injury is where the spine becomes visibly curved off to one side as the disc tries to get away from the nerve it is touching. You will visibly see the person’s spine twisted off to one side.
With a locked facet joint, a simple osteopathic manipulation and a person can get off a treatment couch and have an immediate 60 – 70 % relief of symptoms, the person often being almost back to normal the next day. Disc injuries generally benefit more from medication, although proper physio can also play its part. With a facet joint injury, you are simply unlocking the locked facet joint which limited movement and was causing the problem. With a disc injury, you are trying to take pressure off the disc in the hope that it stops pressing against the nerve. Once off lumbar facet joint manipulation can play it’s part in recovery from disc disorders, if used at the right time by an experienced practitioner. Again this is used to mobilize the area and try and take pressure off the disc.
Often with a suspected disc injury a physio etc. may need to refer a patient to a doctor for a second opinion and most possibly medication( NSAIDs, muscle relaxant, nerve blocker), depending on the level of pain and discomfort. The doctor may also refer the patient for an MRI if they need more information on the level of damage. Physio generally involves deep tissue massage, dry needling, manipulation at the right time, but not endless sessions of this for weeks. A rehab program involving pilates type exercises etc. is paramount once a patient improves. Continuous spinal manipulations several times weekly for extended periods pushed by certain professions could do more harm than good, causing sheering of the disc and slowing healing.
”Putting back in a slipped disc” by manipulation is a myth. When somebody gets a manipulation done, the little crack you hear is when the facet joint gaps or unlocks. It is not the disc going back into place. That is the reason one person gets massive relief from ”the crack” during a manipulation and another person doesn’t. To generalize it is because one person had a locked facet joint, the other had a disc injury. If you look at the diagram of disc disorders above, you will see that the disc is more bulging, protruding or breaking down rather than being out of place.