Pubic symphysis diastasis (PSD) is defined by the excessive separation of the pubic joint, which causes pain and functional impairment. While separation can occur due to direct traumatic injury, it is most frequently associated with the physiological and mechanical stresses of pregnancy and childbirth. PSD is characterized by instability of the pelvic ring, making simple movements difficult for the affected individual. Recognition of this condition is important, as timely management can significantly improve recovery and prevent long-term complications.
Anatomy and Mechanism of Pubic Symphysis Diastasis
The pubic symphysis is a fibrocartilaginous joint connecting the left and right pubic bones at the front of the pelvis. It is composed of a fibrocartilage disc sandwiched between the ends of the pubic bones. The joint is reinforced by four strong ligaments—the superior, inferior, anterior, and posterior pubic ligaments—that keep the joint stable.
Normally, the gap between the two pubic bones in a non-pregnant person measures only 4 to 5 millimeters. The joint allows slight mobility, necessary for absorbing shock and managing forces transferred to the lower limbs. During pregnancy, hormonal changes cause physiological widening up to about 9 millimeters to prepare the pelvis for delivery.
Pubic symphysis diastasis is clinically defined as a separation that radiologically exceeds 10 millimeters, signaling a pathological process rather than normal physiological change. This excessive widening compromises the stabilizing function of the ligaments and fibrocartilage. This structural compromise leads to abnormal motion at the joint, generating shearing forces that result in inflammation and pain.
Common Symptoms and Diagnostic Procedures
The characteristic symptom of pubic symphysis diastasis is severe, sharp pain located directly over the pubic joint in the anterior pelvis. This pain often radiates outward to the lower back, groin, hips, and down the inner thighs. The pain is typically aggravated by activities that require weight-bearing or asymmetrical movements, such as walking, climbing stairs, or turning over in bed.
Patients may report a distinctive mechanical sensation, such as a palpable “clicking,” grinding, or a feeling that the pelvis is splitting open with movement. Ambulation becomes difficult, leading to a noticeable, unsteady “waddling” gait. Instability also causes difficulty with active and passive straight leg raises and an inability to stand on one leg.
Diagnosis begins with a thorough physical examination, including palpation of the pubic symphysis, which often reveals tenderness and sometimes a palpable gap in the joint. Specific stress tests may be performed, such as compressing the greater trochanters toward the midline, which can elicit severe pain, suggesting symphyseal injury. The inability to perform a hip flexion while maintaining knee extension is another sign that can point toward symphyseal instability.
Imaging is necessary to confirm the diagnosis and measure the degree of separation. A pelvic X-ray is considered the standard method for measurement and can be taken in a “flamingo stance”—where the patient bears weight on one leg—to demonstrate instability with a vertical displacement of more than 1 centimeter. Ultrasound and Magnetic Resonance Imaging (MRI) are also used to visualize the extent of the separation and assess associated soft tissue damage, especially when X-rays are avoided, such as during pregnancy.
Primary Causes and Contributing Risk Factors
PSD results from direct trauma or, more commonly, hormonal and mechanical stresses during the peripartum period. During pregnancy, the body produces hormones like relaxin and progesterone that increase the laxity of pelvic ligaments. This hormonal effect, which is adaptive for childbirth, can sometimes lead to excessive joint separation.
The mechanical forces during labor are often the final trigger for diastasis. Factors such as a rapid second stage of labor, a forced or severe abduction of the thighs during delivery, or instrumental assistance like forceps can place overwhelming stress on the already-loosened joint. This excessive strain can lead to a tearing of the fibrocartilaginous disc and the supporting ligaments.
Several factors increase an individual’s susceptibility to developing this condition:
- Previous pelvic trauma.
- Carrying a large infant (fetal macrosomia).
- Multiple gestations.
- A history of previous symphysis pubis dysfunction.
- Connective tissue disorders.
Management Strategies and Recovery Expectations
Management of PSD is conservative, focusing on stabilizing the pelvis, managing pain, and restoring function. The goal is to minimize movement across the joint to allow the ligaments and fibrocartilage to heal. This involves immediate modifications to daily activities, such as using crutches or a walker to avoid full weight-bearing on the affected side.
External support is a cornerstone of treatment, typically involving the use of a pelvic belt or binder worn tightly around the hips to physically compress and stabilize the joint. Physical therapy is then implemented, focusing on strengthening the deep core and pelvic floor muscles to provide internal stabilization. Therapy progresses from non-weight-bearing exercises to controlled dynamic movements, retraining the musculature to support the pelvic girdle.
Pain control is managed with analgesics, often starting with acetaminophen during pregnancy and transitioning to nonsteroidal anti-inflammatory drugs (NSAIDs) postpartum. Patients must avoid activities that involve asymmetrical leg movements, such as stair climbing, standing on one leg, or deep squatting. Most patients experience gradual improvement in pain and symptoms over about six weeks.
While pain relief may begin quickly, full recovery often takes several weeks to months post-injury or post-delivery. In rare cases, typically when separation exceeds 2.5 to 4 centimeters or when conservative treatment fails after four to six weeks, surgical intervention may be considered. Surgery involves open reduction and internal fixation, using plates and screws to stabilize the pubic bones.