Objective To investigate the clinical characteristics and diagnostic methods of lateral partial tears of the rotator cuff bursa. Methods From August 1999 to June 2006, 38 cases of lateral partial tears of the rotator cuff bursa were treated surgically. There were 28 male cases and 10 female cases. The age ranged from 18 to 69 years old, with an average of 45.7 years old. There were 11 cases of left shoulder and 27 cases of right shoulder. According to the Ellman classification criteria, 6 cases were of degree I, 7 cases were of degree II, and 25 cases were of degree III. All 38 patients had preoperative orthogonal and supraspinatus radiographs, 27 had ultrasound, 35 had MRI or MRA, 13 had subacromial decompression and rotator cuff debridement, and 25 had subacromial decompression and rotator cuff repair. Results All 38 cases had shoulder pain, and 18 cases had nocturnal pain. The physical examinations with high positive rates were Neer impingement sign 92.1% (35/38), Hawkins impingement sign 71.1% (27/38), large humeral nodal pressure pain 89.5% (34/38), 60°~120° pain arc sign 68.4% (26/38), and retraction resistance test 68.4% (26/38). According to the Bigliani shoulder crest typing criteria: 2 cases of type I, 26 cases of type II, and 10 cases of type III. The positive detection rate of ultrasound examination was 48.1% (13/27), and the positive detection rate of MR examination was 74.3% (26/35). Conclusion The positive rate of Neer impingement sign and large nodal pressure pain was high in patients with partial tears of the lateral rotator cuff bursa. ultrasound and MR have some value in diagnosing partial tears of the lateral rotator cuff bursa. Arthroscopy remains the most reliable method to diagnose lateral partial rotator cuff bursa tears.