Trochleoplasty has become an accepted surgical solution for patients having recurrent patellar instability, based on the pathomorphology of trochlear dysplasia. Several surgical techniques exist to treat trochlear dysplasia, including arthroscopic deepening trochleoplasty (ADT). Similar to other endoscopic or arthroscopic procedures, it seems to be precise, less invasive with a reduced risk of infection, less painful, reduces the risk of arthrofibrosis and speeds recovery. This article is a detailed description of the procedure that has been slightly modified since the original description. The ADT procedure has now been performed on 56 knees in 39 patients (26 women and 13 men), median age 19 years (range: 12-46 years). An occurrence of a complication (1 deep venous thrombosis) has been noticed. Further surgery was needed for 6 knees. No redislocations have been observed. The indications for the procedure have been expanded to include patients with degenerative changes in the trochlea region and patients with severe trochlea dysplasia without instability suffering from chronic severe anterior knee pain that does not improve after 1 year of physical therapy. The ADT technique, with or without reconstruction of the medial patellofemoral ligament, has been found to be a reproducible and a safe technique without serious complications.