Objective To evaluate the surgical technique and effectiveness of arthroscopic treatment for lateral discoid meniscus injury. Methods Between January 2010 and May 2011, 38 patients (42 knees) with lateral discoid meniscus injuries underwent arthroscopic treatment. There were 23 males (24 knees) and 15 females (18 knees), aged 7-62 years (median, 32.8 years). The disease duration was 7 days to 40 years (median, 8.6 months). According to Watanabe’s classification of discoid meniscus, 22 knees were classified as complete type, 19 knees as incomplete type, and 1 knee as Wrisberg type. Meniscus plasty combined with suture was performed in 25 patients (28 knees), partial meniscectomy in 12 patients (13 knees), and complete meniscectomy in 1 patient (1 knee). After operation, the rehabilitation training programs (including straight-leg-raising exercise and range of motion exercise) were carried out. Results All incisions healed primarily. The patients basically had normal activities after 3-4 weeks. All the patient were followed up 12-18 months (mean, 14.3 months). No joint locked or clicking symptom occurred; no tear or revision was noted during follow-up. At 3 months, 6 months, and 1 year after operation, the range of flexion and extension were significantly improved when compared with ones at preoperation (P lt; 0.05). Based on Ikeuchi’s grading, the results were excellent in 22 knees, good in 16 knees, and fair in 4 knees with an excellent and good rate of 90.4%. The Lysholm score was significantly increased to 88.57 ± 2.95 at immediate, 91.02 ± 4.17 at 3 months, 92.90 ± 3.36 at 6 months, and 94.74 ± 3.52 at 12 months after operation from 69.38 ± 4.59 before operation (P lt; 0.05). C onclusion Treatment of lateral discoid meniscus injury under arthroscopy has the advantages of minor trauma, precise resection or repair meniscus, preservation of more meniscus function, and low incidence of osteoarthritis. If the operation is combined with standard rehabilitation training, the short-term effectiveness can be enhanced.