Chronic patellofemoral instability is a disabling condition and the surgical solutions for this condition have improved due to an increased understanding of the anatomy and pathomorphology of the unstable patellofemoral joint. Since it was demonstrated in 1994 that trochlear dysplasia was present in 85% of the cases with patellofemoral instability , trochleoplasty became an accepted surgical procedure to treat some of these patients. With this procedure, the instability causing factor of missing bony guidance can be addressed by creating a sufficient trochlear grove [4, 7-9]. With this procedure, rather than performing indirect procedures such as transfer of the tuberosity, stability can be provided in more then 20° of flexion without increasing the patellofemoral pressure. However, open trochleoplasty is a major operation and the surgical trauma, the retinacular scar as well as the subcutaneous scar and the postoperative pain seems to be more pronounced compared to other stabilizing methods, leaving the joint intact. Furthermore, compared to arthroscopic procedures open procedures are commonly related to an increased risk of infection and arthrofibrosis . Additionally, patients undergoing the open trochleoplasty need several days of hospitalization to manage the postoperative pain and to initialize the mobilization, as well as a long time to get back to work, all factors that make the procedure relatively expensive. Despite the good clinical results of trochleoplasty, applied in cases with severe trochlear dysplasia and recurrent patellar dislocations, and despite the documentation of normal postoperative cartilage status , a mixture of these above-mentioned circumstances have until now been reluctant factors for surgeons to commence to this operation. Since arthroscopic techniques have continuously improved in orthopedic surgery, and due to the obvious advantages of this minimally invasive surgery such as less pain, faster rehabilitation, shorter hospitalization and less scar formation, these techniques has become more and more favored. Due to the above-mentioned postoperative effects after open trochleoplasty, a need for developing an arthroscopic technique in this situation has also been requested. This, in order to avoid the above-mentioned risks and deficiencies, and therefore provides an accelerated and less painful postoperative phase. With improvement of arthroscopic instruments and devices, this newly developed technique was tested and specified in a series of cadavers before instituting its clinical use in the beginning of 2008. The results have been encouraging with the above-mentioned advantages regarding less pain, faster rehabilitation, shorter hospitalization and less scar formation and at least it has been documented that the technique is possible. We would like to emphasize that it is a technical demanding procedure and there is a need for a longer follow-up. Indication for the arthroscopic trochleoplasty are two or more patellar dislocations with a persistent Fairbank's apprehension sign from 0° to 50° of flexion and trochlear dysplasia grade B to C and eventually also grade D, as defined by Dejour et al. and regraded by Tecklenburg et al. [2,6]. Exclusion criteria are a cartilage defect in the trochlea ICRS grade 3 or 4 with a diameter of 2 mm or more.