Purpose. Our understanding of the spectrum of pathological lesions of the shoulder anterior capsular-labral complex in anterior instability continues to evolve. In a previous study using magnetic resonance arthrography we have showed three variants of the essential lesion of the anterior capsular-labral complex. This is the first large arthroscopic study to finely evaluate the nature and relative proportions of these three lesions in anterior instability. Methods. We studied 122 patients, 101 male and 21 female patients with an average age of 28 (17 to 47 years old), undergoing primary arthroscopic stabilization for anterior instability between 2004 and 2008. The pathoanatomy of the anterior capsule-labral complex was documented. Based on our previous MRI arthrography experience we were able to categorize the lesions seen arthroscopically in three subgroups: the Bankart lesion, the Perthes lesion and the ALPSA (anterior periosteal sleeve avulsion). Results. Arthroscopic findings confirmed the presence of the triad of essential lesion. The relative proportions of the subcategories of the essential lesion were as follows: 71 (58%) Bankart lesions, 18 (15%) Perthes lesions and 33 (27%) ALPSA lesions. Each lesion has unique characteristics, which affect treatment and prognosis. We describe the three types of labral injury and the surgical implications. Conclusion. The literature on the essential anterior capsular-labral lesion has historically focused on the Bankart lesion. There are in fact three variants of the essential lesion: the triad of Bankart, ALPSA and Perthes. This study evaluates these lesions and quantifies their relative proportions in a large series. We believe that awareness of this sub classification of the essential lesion is important as it affects the management of this condition