BackgroundPatients with groin, hip and pelvic pain but normal findings on MRI and minimal changes on x-ray can be a diagnostic problem. This paper looks at the arthroscopic findings of patients who have had hip pain and a positive response to an intra-articular anaesthetic but have non-contributory imaging. We hypothesized that standard MRI’s were missing significant pathology and if there was a response to intra-articular local anaesthesia, pathology found during arthroscopy was likely.MethodsA retrospective review of all hip arthroscopies performed from March 2011 to January 2015 by two orthopaedic surgeons specializing in hip arthroscopy was conducted to identify patients with clinically suspected intra-articular hip pathology despite a normal MRI report and X-ray. Clinical suspicion of intra-articular hip pathology was confirmed with a positive response to a fluoroscopically guided intra-articular injection of local anaesthetic and corticosteroid. Pathologic findings were collated from the standardised operative notes.ResultsFifty-three hip arthroscopies performed in 51 patients met the inclusion criteria from a total of 1348 hip arthroscopies performed over a 46-month period. All but one of the 53 (98%) hips had arthroscopically confirmed pathology. Mean patient age was 32.5 years [15 to 67 years] with 40 (78%) females and 11 (22%) males. 92.5% of the hips (49/53) were FADIR (flexion, adduction and internal rotation) positive on clinical examination, giving this test a positive predictive value of 98% (95% CI: 89.31 to 99.67%) for intra-articular pathology.ConclusionsIn patients with a normal MRI without contrast and a positive response (relief of pain) to an intra-articular injection that failed conservative management, there is a 98% chance of intra-articular hip pathology being discovered on hip arthroscopy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-017-1485-5) contains supplementary material, which is available to authorized users.