The purpose of this study was to develop a new arthroscopic approach for traumatic instability that effectively reattaches avulsed capsulolabral tissue to the glenoid articular rim with sutures. This technique does not depend on fixation devices, trans-scapular drilling, or implantation of suture anchors. We attached a three-dimensional position sensor and force and torque transducer to the humerus and scapula of eight normal cadaveric shoulders to measure the normal, surgically unstable (arthroscopic Bankart lesion), and repaired preparations. We assessed eight motion ranges and six laxity tests. Capsulolabral release increased all passive ranges and allowed significant translational increases on posterior drawer and crank testing. After repair, motion was never decreased and there were no differences in laxity relative to normal. Neurovascular structures were never at risk. Our arthroscopic repair provides anatomic reattachment and effective deepening of the glenoid con-cavity similar to that achieved by open repair. This new method restores joint stability, preserves motion, and can withstand forceful loads. Ongoing clinical trials will substantiate whether the technique is as safe and reliable as shown cadaverically.