Endometriosis is a condition where tissue similar to the lining of the uterus grows outside the uterine cavity, most commonly in the pelvis. This tissue can lead to chronic inflammation, scarring, and the formation of lesions, often resulting in significant pain. Endometriosis can cause groin pain because the disease often involves structures and nerves connecting the pelvis to the lower extremities. This pain is typically referred pain, where irritation in the pelvis is perceived as originating in the groin or inner thigh.
How Pelvic Implants Lead to Groin Pain
The mechanism for endometriosis-related groin pain centers on the location of the endometrial lesions and their interaction with the pelvic nervous system. Lesions often implant on or near sensitive structures like the uterosacral ligaments, the pelvic sidewall, and the pelvic fascia. These areas are densely populated with nerves that transmit sensory information from the pelvis to the spine and brain.
Inflammation and scar tissue around these implants can irritate or physically entrap nearby nerves. The obturator nerve is frequently implicated, as it runs through the pelvis and innervates the muscles of the inner thigh and the skin of the groin area. When inflamed implants press upon this nerve, the pain signal is incorrectly interpreted as originating in the groin or inner thigh.
The genitofemoral nerve is another pathway whose irritation by deep infiltrating endometriosis (DIE) can lead to groin pain. Compression of this nerve, which provides sensation to the upper anterior thigh and genital area, can cause a burning or aching sensation that radiates into the groin. Chronic inflammation can also lead to hypertonicity of the pelvic floor muscles, which pull on and irritate surrounding tissues, contributing to pain felt in the hip and groin region.
The Characteristics of Endometriosis-Related Groin Pain
Groin pain caused by endometriosis is often cyclical, typically worsening during the premenstrual and menstrual phases. This pattern occurs because the ectopic endometrial tissue responds to hormonal fluctuations, leading to inflammation and bleeding within the lesions, similar to the uterine lining.
The pain can be unilateral, affecting one side, or bilateral, involving both sides of the inner thigh and groin area. While some patients experience intermittent pain correlating with their cycle, others suffer from a constant, deep ache, particularly with deep infiltrating endometriosis. This constant pain is often due to extensive scarring or persistent nerve irritation that remains active outside the menstrual window.
Groin pain often co-occurs with other symptoms typical of deep pelvic involvement. These may include deep pain during sexual intercourse (deep dyspareunia), or specific bowel and bladder symptoms, such as painful bowel movements or increased urinary urgency. These combined symptoms help specialists link the groin discomfort back to the underlying pelvic condition.
Other Potential Causes of Groin Pain
Groin pain can arise from many sources, making a proper differential diagnosis important. Musculoskeletal issues are the most frequent alternative cause, including adductor muscle strains or tears, common in physically active individuals. Hip joint pathology, such as labral tears or osteoarthritis, can also refer a deep, aching pain into the groin.
Inguinal or femoral hernias are another common cause, presenting as a bulge or mass that causes pain, often exacerbated by activities that increase abdominal pressure like coughing or lifting. Nerve entrapment syndromes unrelated to pelvic endometriosis can mimic the pain, such as meralgia paresthetica, which involves the compression of the lateral femoral cutaneous nerve. Non-gynecological visceral causes, like kidney stones or urinary tract infections, can also present with pain that radiates into the groin area.
Medical Evaluation and Next Steps
Individuals experiencing chronic or cyclical groin pain, especially when accompanied by painful periods or deep dyspareunia, should seek evaluation from a healthcare provider specializing in pelvic pain. Detailed symptom tracking, noting the timing and intensity of the groin pain in relation to the menstrual cycle, provides valuable diagnostic clues. The initial evaluation involves a thorough physical examination to check for tender points, muscle tightness, and any palpable masses in the groin or pelvis.
Imaging studies are often the next step in the diagnostic process. A specialized transvaginal ultrasound or a magnetic resonance imaging (MRI) scan can look for deep endometrial nodules or scar tissue located near pelvic nerves, such as the obturator nerve. While imaging can provide strong evidence, diagnostic laparoscopy remains the definitive standard for confirming the presence and extent of endometriosis.
Treatment focuses on managing the underlying disease. Hormonal suppression therapies are frequently employed to reduce the growth and activity of endometrial implants, which can decrease inflammation and nerve irritation. For cases where deep implants cause nerve compression, specialized excision surgery may be necessary to remove the lesions and free the entrapped nerve, offering a long-term solution to persistent pain.