What are the characteristics and causes of coccydynia?
There are a lot of possibilities in regards to the causes of coccydynia. I would say the most common, at least that I see walking into the clinic, is trauma. Trauma to that area can include vaginal delivery, especially instrument-assisted or shoulder dystocia. A fall is very common. I live in Missouri and it's very common for people to slip on ice because we often have ice first or rain first (which will freeze) and then snow on top of it so that people can't necessarily see that there's ice under the snow. Therefore, we have a lot of coccydynia due to falls. A near fall can also cause coccydynia. The reason for that is that when you slip and try really hard to catch yourself, those muscles activate and sometimes that can set off a muscle spasm or some other problems that can lead to coccydynia. Certainly, a direct blow can cause coccydynia, but that is one of the less common ways that I actually see people being injured. Water slides are such common causes of coccydynia that there are entire articles looking at incidents of coccydynia that start after a person went down a water slide.
Another possible cause would be repetitive microtrauma. For example, sitting on hard surfaces for long periods of time or just sitting awkwardly with poor body mechanics. You certainly could also have repetitive microtrauma from not balancing your musculature and balancing intra-abdominal pressure ideally as well. That wouldn't necessarily be related to sitting, that would be more so with activity.
A pelvic floor spasm is a very likely cause of coccydynia, especially if that spasm is unilateral resulting in uneven pressure across the tailbone. Scar tissue from a pilonidal cyst removal or a coccygectomy is another cause. Idiopathic coccydynia is actually fairly common as well, meaning we just don't know what started it. Those ones, unfortunately, have the least ideal prognosis. Rapid weight loss is also a common cause of coccydynia, and most people think that this is just due to shifting pressures. Often people who lose weight very rapidly are losing a lot of muscle mass as well as fat and water. Finally, pelvic organ prolapse is also a very common cause of coccydynia.
Characteristics of coccydynia include pain with sitting, pain that is typically worse with leaning back and also worse with sitting on really hard surfaces, and interestingly, it's actually often also worse with sitting on a very, very soft surface. So there's a happy medium in there somewhere that is more comfortable for people. It might be actually better if they're sitting on a toilet, or a donut cushion and the reason for that is that both of those will actually unweight the coccyx to where they're sitting more on their ischial tuberosity. They will often have pain with transitions, especially transitions where they're going from a lot of hip flexion to not very much hip flexion, or the reverse, so sit to stand, stand to sit. Usually, the pain will improve some with walking or any kind of repetitive low impact movement. Patients with coccydynia often will have pain with bowel movements and sometimes will have pain with sex, especially with the penetrative aspect of sex.