A Hill-Sachs lesion greater than 20% of the humeral cartilage is thought to be a surgical indication. However, there have been no anatomical or biomechanical reports. The purpose of this study was to determine the contact between the glenoid and the humeral head to obtain a clue for surgical indication. We used nine freshfrozen cadaveric shoulders (mean,71 years old). The specimen was fixed to a shoulder-positioning device. A 22-N force was applied to the humeral head. The insertion of the supraspinatus tendon, the infraspinatus tendon, and the teres minor tendon was sectioned. Anterior structures such as the glenohumeral ligaments and the subscapularis tendon were preserved. The entire rim of the glenoid was marked on the humeral head using a Kirschner wire with the arm in maximum external rotation and horizontal abduction. This marking was repeated with the arm in 0°,30° and 60° of abduction. The distances from the contact area to the edge of the articular surface of the humeral head and to the footprint on the greater tuberosity were measured by a digital caliper. With an increase in arm elevation, the. glenoid shifted from infero-medial to supero-lateral direction, creating a band-like zone along the rim of the articular humeral cartilage. We named this zone a “glenoid track”. When a Hill-Sachs lesion exceeds the “glenoid track”, there is a risk of engagement and dislocation. The width of the “glenoid track” (0°,30° and 60° of abduction ) was 17.0 ± 6.6 mm,162 ± 62 mm, and 15.8 ± 2.5 mm from the humeral articular cartilage edge and 18.4 ± 2.5 mm from the foot print or 84 ± 14% of the glenoid width. Hill-Sachs lesion which exceeds 84% of the glenoid width has a risk of engagement and dislocation.