We hypothesize that NSAID prophylaxis of HO may have a role in hip arthroscopy for the treatment of femoroacetabular impingement. All NSAIDs tested, with the exception of aspirin, have resulted in significant decreases in the incidence of HO following hip surgery including less potent regimens such as ibuprofen 1200 mg/day. Naproxen offers the advantage of twice daily dosing with similar potency to ibuprofen. It is readily available and inexpensive. Furthermore, in an unpublished series of 50 patients prescribed naproxen following hip arthroscopy for FAI, we have had no cases of HO at 6 month follow up compared to a 5-10% rate in patients who received no prophylaxis. We propose testing our hypothesis that perioperative naproxen will reduce the incidence of HO following hip arthroscopy in a placebo controlled, double-blinded, randomized controlled trial.