Coccydynia (or a painful coccyx) presents as pain isolated to the tailbone only. The coccyx is the very end of the tailbone. Most individuals with coccydynia are uncomfortable when sitting, especially when sitting directly on the tailbone, and may be uncomfortable when lying down flat on the back because of the pressure this position places on the tailbone. Laying on one side or the stomach is more tolerable. The most comfortable positions for a person with coccydynia are usually standing or walking, positions that relieve the pressure on the tailbone. However, in a patient with a severely irritated coccyx, the motion of walking may further irritate the soft tissues and cause worsening pain.
Coccydynia typically is not associated with leg pain. In the situation of leg pain, especially pain that travels below the knee in a radicular pattern (pain that shoots down the leg in the distribution of a nerve root), other sources of pain should be investigated, such as a disc herniation.
The key to making the diagnosis of coccydynia is a thorough history and physical examination. A physician can localize the area of greatest discomfort to the coccyx and rule out other sources of pain.
WHO GETS COCCYDYNIA AND WHY?
Two causes of coccydynia exist. The most common cause is trauma to the area. Most of the time an individual with coccydynia incurred a specific injury, either directly falling on the tailbone with great force or being hit directly on the tailbone. Sometimes the patient does not recall the injury until direct questioning. The reason behind the pain in individuals who incurred a direct injury to the coccyx is a strain of the sacralcoccyx junction or a broken coccyx. If the pain decreases with time, then the bone is healing and the problem is being solved by Mother Nature. If the pain continues unabated or worsens, then the bone is not healing properly (a fibrous union), or has not healed at all (a non-union).
The second cause of coccydynia is congenital (the patient is born with an abnormal coccyx). The coccyx is a remnant of a tail from a time in which man was less evolved (apes) that has not yet been fully lost in our evolution. At this time, it serves no function for bipeds (beings that walk upright with two feet) that has been identified by anatomists. The coccyx typically fuses to the rest of the spine as part of the normal human anatomy. However, in some patients it remains a separate bony fragment. Over time, if enough motion occurs between the unfused portion of the coccyx and the remainder of the spine, pain can occur. Some individuals with an unfused coccyx will never experience pain in the area, while others will. It is impossible to predict which individuals with unfused coccyx will experience pain.
One common event, which can begin the pain cycle in patients with an unfused coccyx, is pregnancy. Most likely the stress of vaginal delivery and also the extra pressure on the coccyx during pregnancy irritate an unfused coccyx.
The primary symptom of degenerative disc disease (or internal disc disruption) is midline back pain. Individuals with DDD often experience “referred pain” in the buttocks, pelvis (iliac crests), sacroiliac joints (felt in back of the hips), and the back of the thighs. A referred pain is one that stems from a structure, in this case the disc, but is felt a short distance away. Pain associated with DDD is greater when sitting and standing than when lying down, which decreases the pressure on the degenerating disc. Individuals with DDD usually have difficulty finding a comfortable position when sitting or standing, and constantly have to change positions. Bending and lifting, especially heavy items, aggravate the pain and rising from a chair may be problematic. Although the pain associated with DDD may be felt while walking, it is usually not aggravated by prolonged walks.
In addition to the above, in more severe cases of DDD, individuals may experience symptoms of sciatica or a pinched nerve root, similar to that experienced by an individual with a herniated or slipped disc. The degenerating disc collapsing and causing a nerve root to be pinched causes these additional symptoms.
WHO GETS DEGENERATIVE DISC DISEASE AND WHY
Discs are the cartilage that lies between the bony vertebral bodies of the spine. Since motion occurs in this area, these are considered a joint. As a natural phenomenon of the aging process, discs lose their water content and degenerate. Concurrently, tears occur in the outer lining of the disc (the annulus). In adults, the annulus has nerve fibers while the center of a disc does not. A tear in this outer annulus can be quite painful. Although these degenerative processes are part of the natural aging of the spine, the discs of some people degenerate much more quickly than others. Also, for reasons as yet unknown, some individuals experience much more pain from these degenerative changes than others (see section under imaging studies about results of MRI).
The symptoms of DDD typically follow one of three courses:
- a significant injury followed by sudden and unexpected back pain;
- a trivial injury accompanied by significant back pain; and
- a gradual onset and worsening of midline low back pain;
- Sudden and unexpected back pain following a significant injury: Some individuals can identify specific episodes (such as weight lifting, a fall onto the legs or buttocks, or a sudden twisting motion) immediately preceding the onset of back pain. For these individuals, the sudden or unexpected episode may have brought to light an already degenerating disc or caused a new annular tear to a degenerated disc. The unexpected incidents are usually of a form that causes vertical pressure upon the spine, compressing or pushing together the disc space. Examples include jumping onto your feet from a height, or putting weight on your head. This form of compression is often referred to as “axial load”.
- Trivial injury accompanied by significant back pain: A second group of individuals incur a trivial injury to their back, often work-related. These individuals typically have a history of significant DDD with symptoms that were less severe than those accompanying the new injury.
- Gradual onset and worsening of midline low back pain: A final group of individuals cannot specifically remember an accident that caused the pain to begin. Instead, the pain worsened gradually as the disc degenerated.
A genetic predisposition to having bad discs is the most common risk factor for DDD. The second most highly correlated risk factor for developing DDD is a history of smoking. Job-related risk factors include activities that place physical pressure on the back, such as handling particularly heavy material, repeated lifting while in the upright position (assembly line and manual laborers), and being subjected to vehicular vibration (truck drivers). Leisure activities that repetitively place strain on the back have also been implicated in causing DDD. By example, recent studies have identified an increased incidence of DDD among elite soccer players, golf players and competitive weight lifters.