Trigger point "dry needling" is a technique used to treat myofascial pain. It involves using filiform needles which are inserted into muscles to give local pain relief. Few cases of serious adverse events following this treatment have been reported in the literature. In this paper we describe the case of a professional swimmer who developed pneumothorax after dry needling treatment and discuss the medicolegal and ethical aspects related to competencies and responsibilities of medical doctors and physiotherapists performing the procedure.