Pectoralis major (PM) rupture is a severe injury that untreated can lead to a profound functional deficit. Early surgical repair can greatly improve outcomes and give a more predictable timetable for recovery, making this the goal of current treatment. Surgical intervention is also essential to return professional athletes to their previous level of competition. However, there is no single, reliable and easily reproducible test that can be used to establish the diagnosis. We describe 'The Cruciform Test'; a method of identifying PM rupture that can be used for initial diagnosis either in clinic or a pitch-side environment, or to assess restoration of normal anatomy and function post-operatively. We studied a series of 14 patients who underwent open PM repair in order to evaluate this method of assessment. All patients had a positive test pre-operatively. 5 were formally tested at post-operative follow-up and all had a negative result. The Cruciform Test is a simple and reproducible diagnostic tool that has potential as a clinical indicator of both PM rupture and successful repair. It can therefore contribute to earlier diagnosis, prompt surgical intervention and facilitate return to play at the earliest opportunity.