What Three Things Contribute to Facet Degeneration and Facet Joint Syndrome
The body exists in one of two states, in control and out-of-control. Over thousands of years, the people that survived most successfully were those whose spine would be protected whether the body was completely in control or not. The facet joints of the spine are the perfect example of how the body has adapted and been shaped for survival over the millennia. Current sedentary lifestyles have not been around that long and we can see that the facet joints developed as strong protectors of the spine.
The motions of the spine are a complex combination of rotation and forward-backward translation. The facets on the posterior side of the spine act in harmony with the intervertebral disc and on the front (anterior column) of the spine. Goals of the facet joints are to provide a safe range of motion, information about position in 3-D space and protect the nerves traveling through the spinal column.
When the body is in control, the primary restraints to excessive motion are the muscles. They do a great job of providing progressive resistance to excessive ranges of motion as well as giving the body feedback about where it is in space. This sophisticated control system of muscular restraint is likened to a set of springs that act in harmony to produce motion and restraint, sometimes simultaneously. Of course this is why core strengthening is so important for comfort, function and stability of the spine in general.
So what happens if the muscles can’t control and restrain the spine motion adequately?
The next level of restraint for the facets after the muscles is the capsule of the facet joint. The capsule is thick and filled with nerves. It is tightly wrapped around the facet joint to hold the joint together, maintain alignment, provides information about where the back is in 3 dimensional space and acts to contain the synovial fluid inside the joint. Stability beyond muscular control relies on the structural integrity of the thick capsule, which is substantial. The problem with using the capsule as a restraint is that if it gets torn or stretched, it may never heal back to its original shape or structural integrity. This means that after healing does occur, the facet joint can slide into a position that is not in perfect alignment and the process of facet degeneration can occur and can progress to facet joint syndrome. Severe pain can occur with capsular injury because of the dense nerve supply. Healing of the capsule can be slow because it has a relatively poor blood supply (compared to muscles) and it never gets a chance to hold still and heal. If pain is severe enough, then the muscles will also stop working or spasm in an effort to reduce back motion. This can lead to deconditioning of the muscles that need to be retrained when the pain resolves.
So what happens if the muscles and capsule can’t control and restrain the spine motion adequately?
In this case the body is usually out of control and motions are no longer under muscular control and the capsular soft tissues have ruptured. This is the situation with any high-energy event like an automobile accident or any other high speed accident. The bone of the facets provides the final level of restraint after muscle and capsular restraint has failed. The facet bone is the bony stop of the facet structure. Even though the facet joints are covered with cartilage, the cartilage is just a thin covering of the bone. Any loss or injury of the cartilage can result in facet degeneration or painful facet syndrome. The facet bone acts as the final restraint against excessive motion in flexion, extension, and axial rotation. If extreme forces occur and this final bony restraint is exceeded by fracture or dislocation, then injury to the spinal cord can occur.