الفهرس 
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Abstract
Patellar instability is a generic term that is used to describe patellar dislocation, patellar subluxation, and general symptomatic instability. Patellofemoral instability is a relatively difficult condition to treat; accurate management of the condition should take into account the anatomy of the joint and its stabilizing structures. The goal of any treatment should be to restore the normal anatomy of the joint. It is important to understand the basic anatomy and biomechanics of this condition, the classification of different types of patellar instability, varying presentations, and diagnostic techniques and criteria, including the types of imaging studies that can be useful in determining the ultimate course of treatment (102).
The role of arthroscopy as a diagnostic tool is valuable for resistant cases or circumstances in which surgery is contemplated (10,69,120). It should be a part of examination before any operation for realignment whatever its type (129). It’s superior, even to MRI in chondral lesion detection as it permits a visual inspection and palpation of the suspected lesion. Also it allows visualization of patella tracking (125).
With acute dislocation, most authors prefer conservative management (1,166) after performing of MRI, the best investigation of MPFL lesion beside chondral lesions (68,117). Conservative management focuses on exercises to strengthen the quadriceps, and especially the vastus medialis, to prevent further instability (56). However, some controversy exists about the operative treatment in acute dislocation. The indications of operative treatment of acute dislocation as following 1) Evidence on imaging or clinical examination of osteochondral fracture or major chondral injury; 2)Palpable or MRI findings of substantial disruption of the MPFL VMO-adductor mechanism; (27,166,158) . 3) A patella laterally subluxated on the plain Merchant view with normal alignment on the contralateral knee; 4) A patient fails to improve with nonoperative management; and 5) Subsequent redislocation (166).
Arthroscopic MRP can be used as operative treatment of acute dislocation. Mariani et al, 2011 described an Arthroscopic technique for patellar reinsertion of the MPFL in acute patellar dislocations (108). No studies, according to our knowledge, compare between open and arthroscopic procedures as a treatment for acute patellar dislocation(30).