Fortunately, complications after hip arthroscopy are quite rare. Others have reported in the medical literature their experience with infection, blood clot, persistent pain, fractures, stiffness or numbness. You may or may not know, however, that similar complications, and even perhaps more problems, can be observed after OPEN surgery for hip impingement (aka Femoral Acetabular Impingement). Open surgery involves a large incision over the hip and requires the hip be dislocated fully out of the socket during surgery. Some surgeons still perform this procedure.
In a recent article in the Journal of Arthroscopy, March 2011, a significant number of patients who had persistent groin pain after open hip osteochondroplasty (shaving of the bone/cartilage on the neck of the femur for CAM impingement) had adhesions/scar tissue build up inside their hip joint. The surgeons went back in to their hips, but this time with arthroscopic surgery, and cleaned out the scar tissue and adhesions between the capsule and the bone. 18 out of 21 of those specific patients got better.