Measurement of the glenoscapular angle (glenoid version) and the percentage of posterior subluxation of the humeral head. To measure the glenoscapular angle, a line is drawn parallel to the scapula and a second line is drawn tangential to the joint. The second line connects the anterior and posterior margins of the glenoid. On MR images, the cartilaginous margins are used. On CT scans, the osseous margins are used. The intersecting line connects the center point of the first line (approximately the middle of the glenoid fossa) and the medial aspect of the scapula. The angle in the posterior medial quadrant (arrow) is measured with a goniometer; 90 degrees is subtracted from this measurement to determine glenoid version. The percentage of posterior subluxation is measured by defining the percentage of the humeral head that is anterior to the same scapular line. The greatest circumference of the head is measured as the distance from the scapular line to the anterior portion of the head. This ratio (the distance to the anterior aspect of the humeral head [AB] divided by the circumference of the humeral had [AC], multiplied by 100) is the percentage of subluxation.