Low Back Pain – Facet vs Disc
Two of the most common causes of low back pain presenting in clinic are discogenic (disc) and facet joint related pain. Injury to either can cause severe discomfort, limiting a person’s ability to carry out normal daily activities. Facet joints are small articulations along each segment at the back of the spine, and help control the movement of the spine. There are two of these joints at each vertebral level. There are intervertebral discs between each level and these act as primary shock absorbers. They are generally between a quarter and a half inch in height, interconnecting the bodies of the vertebral segments. 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 when a lumbar facet joint locks is an increase in pain on extension of the lower back. Basically there is more pain when you try and straighten up your lower back or lean back on it. This position loads pressure on the locked lumbar facet joints. Usually with 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 can give a person an immediate 60 – 70 % relief from pain symptoms. The person is often almost back to normal the next day. With a facet joint injury, you are simply unlocking the locked facet joint in which the 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, spinal manipulation at the right time. A rehab program involving pilates type exercises and some gentle stretching exercises etc. is paramount once a patient starts to improve. Continuous spinal manipulations several times a week 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. Sometimes unlocking a facet joint in the area, if it has locked up say due to muscle spasm etc. can help take pressure of the disc in the area.