Sit bone pain refers to discomfort centered around the ischial tuberosities, the bony prominences located at the base of the pelvis. This type of pain is a frequent concern, affecting many individuals, and can arise from a variety of distinct sources. This discomfort often becomes noticeable during or after periods of sitting.
Understanding the Ischial Tuberosities
The ischial tuberosities are the rounded bones that form the lowest part of the pelvis. These structures are often called “sit bones” or “sitting bones” because they bear a significant portion of the body’s weight when a person is seated. Their anatomical position makes them susceptible to pressure and various types of pain. Several important soft tissues, including muscles and ligaments, attach directly to these bony prominences.
Causes from Direct Pressure and Overuse
One common source of sit bone pain stems from direct pressure and repetitive strain on the area. Prolonged sitting, especially on hard surfaces, can lead to irritation and inflammation. Activities such as cycling, which involves sustained pressure on the sit bones, or other activities with repeated impact can also contribute to this discomfort. This constant mechanical stress can inflame the bursae, which are small fluid-filled sacs that cushion the bones and tendons. This condition, known as ischial bursitis, causes pain and swelling in the sit bones, often described as a deep ache that worsens with sitting.
Muscle and Tendon Related Issues
Pain around the sit bones can frequently originate from issues involving the muscles and tendons that attach to or surround the ischial tuberosities. Hamstring tendinopathy involves inflammation or degeneration of the hamstring tendons near their origin point on the ischial tuberosity. These muscles run down the back of the thigh and are prone to injury from repetitive activities like running, cycling, or hill climbing. Symptoms often include a deep buttock pain that can intensify with prolonged sitting or physical activity, along with stiffness in the affected area.
Piriformis syndrome involves the piriformis muscle, which is located deep in the buttock and can irritate the nearby sciatic nerve. While not directly a sit bone issue, its proximity can cause pain that radiates into the region. The piriformis muscle’s tightness or spasm can mimic sciatic pain, affecting the area around the sit bone.
Nerve Compression and Irritation
Nerve involvement represents another significant cause of sit bone pain, often characterized by radiating discomfort. Sciatica, for example, results from compression or irritation of the sciatic nerve, which extends from the lower back through the buttocks and down each leg. This irritation can manifest as pain near the sit bone, frequently extending down the back of the thigh or leg. Symptoms can range from a mild ache to a sharp, burning sensation, sometimes accompanied by tingling, numbness, or muscle weakness. Common causes include a herniated disc in the spine, bone overgrowth, or even piriformis syndrome.
Another nerve-related condition is pudendal neuralgia, which involves irritation of the pudendal nerve. This nerve exits the pelvis near the ischial tuberosity. Pain from pudendal neuralgia is often described as burning, electric shock-like, or aching in the pelvic area, and it typically worsens with sitting. Prolonged sitting, cycling, or even childbirth can contribute to the development of this nerve irritation.
Other Contributing Factors
Beyond the more common causes, several other factors can contribute to sit bone pain. Stress fractures of the ischial tuberosity, though uncommon, can occur from repetitive stress or overuse, particularly in athletes. Forceful hip flexion or strong muscle contractions can place excessive strain on the bone, potentially leading to these fractures.
Referred pain, originating from structures located away from the sit bone, can also be perceived in this area. Issues with the sacroiliac joints, which connect the spine to the pelvis, or problems within the hip joint itself, such as labral tears or instability, can cause discomfort that is felt around the ischial tuberosities. Additionally, lower back injuries, including disc bulges or herniations, can irritate nerves that refer pain to the sit bone region. While less common directly at the sit bone, arthritis in nearby joints can also be a source of discomfort.