Editorial Commentary: What Exactly Is Impingement—Can Dynamic Magnetic Resonance Imaging “See” Impingement in Femoroacetabular Impingement?

The diagnosis of femoroacetabular impingement (FAI) syndrome requires that 3 prerequisites are met. Patient symptoms and physical examination must be combined with imaging to appropriately make the diagnosis. Imaging, including plain radiographs, magnetic resonance imaging (MRI), and computed tomography, should be interpreted in the context of a high prevalence of cam and pincer morphology, in addition to labral injury, in the general population. All images routinely obtained in current clinical practice are 2-dimensional representations of complex 3-dimensional processes. Although computerized modeling can dynamically manipulate femur and pelvis independently in fluoroscopy-, computed tomography-, and/or MRI-based collision detection models, the exact definition of "impingement" eludes the current literature. High-resolution, high magnet strength (minimum 3 Tesla), physiologic and/or biochemical dynamic MRI has the potential to image both soft and osseous tissues, interacting to best define hip impingement.