Editorial Commentary: The Cause of Groin Pain Is Difficult to Determine: The Elusive "Nether-Nether Region".

As one of the many causes of groin pain, iliopsoas tendinitis can be hard to identify and even harder to treat. It occurs in the setting of both the native hip joint and following total hip arthroplasty. Internal snapping, or coxa saltans, can result from the iliopsoas snapping over the anterior hip capsule or iliopectineal eminence and can be a source of labral pathology. The snapping can be painful or painless. Iliopsoas impingement over total hip components either from the cup or collar of a femoral stem are causes of anterior groin pain. However, there are multiple other causes of groin pain, both intra- and extra-articular, that can make finding the source of the pain difficult. Referred pain from the spine, gynecologic, and gastrointestinal systems can all cause pain in the groin. Core muscle injuries and athletic pubalgia can all cause groin pain and frequently mimic intra-articular hip pathology or iliopsoas tendinopathy. Ultrasound-guided diagnostic injection into the iliopsoas bursa or the juxtaposed hip joint (intra-articular injection) can be helpful in differentiating the source of the pain. Combining a clear history, detailed physical, basic and advanced imaging, as well as diagnostic injection is essential in diagnosing this elusive entity and guiding appropriate treatment.