Fig. (1) Femoro-acetabular impingement. Pincer-impingement is caused by oversized acetabular coverage of the femoral head due to different pathoanatomy such as 1. Acetabular protrusion, 2. An enlarged labrum or osteophytes of the acetabular rim and 3. Focal/global acetabular retroversion. On the right: Cam-impingement with an aspherical femoral head and an enlargement of the femoral neck. Reproduced with permission from OrthoInfo^© American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org.