This symposium contains 12 studies we believe will improve our understanding of recurrent dislocation following total hip arthroplasty (THA). We currently teach residents the incidence of this dreaded complication has decreased to under 1%. Nevertheless, we have evidence from registries and honest surgeons contributing to this symposium that the true incidence is higher. We are constantly reminded of the gravity of the problem when patients who have been in and out of emergency rooms several times recently show up in our offices. Sometimes they are our patients but often they are the patients of another surgeon. Thus, the original surgeon often does not learn his or her patient has dislocated their reconstructed hip or perhaps redislocated them. Patients with recurrent THA dislocations sit on ticking time bombs … and they never know quite when they will go off. The classic article by Nas Eftekhar, MD, “Dislocation and Instability Complicating Low Friction Arthroplasty of the Hip Joint” (CORR 1976;121:120-125 ) is important because it reminds us dislocation is primarily a problem of component malposition and soft tissue tension. Both of these problems are lessened through the employment of a transtrochanteric approach (excellent exposure and ability to precisely and selectively advance the trochanter), which has essentially been abandoned. The 22-mm Charnley head dislocated only 0.5% of the time in this series of 1400 patients. Non-voluntary “joint registries” are an excellent source of demographic data about dislocation following THA. Meek et al found from the Scottish National arthroplasty registry a 1.9% dislocation rate. From the Kaiser Permanente joint registry in California (almost 2000 THAs), Khatod et al identified a 1.7% rate following primary THA and a 5.1% rate following revision. Hartman and Garvin suggest two stage reimplantation for infection can increase the risk of dislocation nearly tenfold. Structured reviews of the literature have become an increasingly useful method of learning more from what others have reported over the years. Battaglia et al confirmed our suspicions that higher volume surgeons witness fewer dislocations in their patients. Likewise, Kwon et al confirmed what many have reported for years: the posterior approach for THA carries the greatest risk of dislocation (compared with anterior and direct lateral approaches); however, the news is not so bleak because there is now a growing body of evidence that when a soft tissue repair is performed, this risk of dislocation drops eightfold to under 0.5%. Iorio et al demonstrate the use of an enhanced posterior soft tissue repair (EPSTR) decreased the risk of dislocation fourfold to 1.3%, an effect which was not improved upon by the use of less invasive surgery. The integrity of the EPSTR can now be assessed by ultrasound as demonstrated by Edwin Su et al. The concept of head-to-neck ratio was considered important prior to the publication of the CORR article of 1976 by Eftekhar, but further evidence and clarification is put forward in this issue. Padgett et al report an elegant study where virtual range of motion (using virtual neckliner impingement as an endpoint) has been explored with a computer aided design (CAD) program for several commonly available hip designs. This virtual work draws attention to the poor range of motion characteristics of the small head-neck ratio of the “Type II taper”. This relationship was confirmed (with remarkable consistency) through a side-by-side single surgeon/institution clinical review of a series of 254 patients: 3.6% risk of dislocation for the 28-mm head, 4.8% for the 26-mm head and 18.8% for the 22-mm head. Simultaneously, Geller et al report on the excellent early wear characteristics of chrome cobalt 32-mm heads articulating in vivo with one version of highly cross-linked polyethylene. This lowers the threshold that the surgeon may have to employ a 32-mm head more routinely (especially when considered next to the Khatod et al data which showed 32-mm heads to help avoid dislocation compared with 28-mm heads). The ideal way to manage THA dislocation is to avoid it as the first order of business. Nevertheless, in the future, more data will need to be collected and presented about surgical and nonsurgical treatment of recurrent dislocation following THA, as has been done by Parvizi et al and Berend et al in the symposium. We hope the readership finds this symposium as useful and important as we believe it to be. We thank the staff at Clinical Orthopaedics and Related Research and the efforts of many reviewers who volunteered their time to ensure the quality of the work we present. William Macaulay, MD Center for Hip and Knee Replacement, Columbia University Medical Center, New York, NY Khaled Saleh, MD, MSc(Epid), FRCSC, FACS Department of Orthopaedic Surgery, University of Virginia, Charlottesville, VA Javad Parvizi, MD Department of Orthopaedic Surgery, Rothman Institute at Thomas Jefferson University, Philadelphia, PA