Objective To observe the outcome of arthroscopic meniscal plasty and suture repair to treat torn discoid lateral meniscus involving popl iteal hiatus. Methods Between January 2008 and May 2009, 21 cases of torn discoid lateral meniscus involving popl iteal hiatus were treated by arthroscopic surgery. There were 9 males and 12 females with an average ageof 22.5 years (range, 12-45 years), including 12 left knees and 9 right knees. Seven cases had the history of injury and other 14 cases had uncertain trauma. The average disease duration was 6.4 months (range, 3 months to 2 years). All patients complained knee pain or locking with positive McMurray test and mill ing test before surgery. All cases had torn discoid lateral meniscus, and the tear extended to the popl iteal hiatus, including 17 cases of complete type and 4 cases of incomplete type according to the Watanabe classification. After meniscal plasty, suture repair of torn popl iteal lateral hiatus was performed. The anterior part to hiatus was repaired by the outside-in technique, and the posterior part underwent repair of all inside technique by FasTFix. Results All wounds healed by first intention with no compl ications such as infection, stiffness of knee, or injury of common peroneal nerve. All patients were followed up 12-28 months with an average of 18 months. The symptoms of knee pain or locking disappeared postoperatively with negative McMurray test and mill ing test in all patients. The Lysholm score was improved from 54.0 ± 13.4 to 90.0 ± 6.6 at 12 months postoperatively, showing significant difference (t=— 12.00, P=0.00). Based on the improved Lysholm classification standard, the results were excellent in 14 cases, good in 5, and fair in 2; the excellent and good rate was 90.5%. Conclusion For torn discoid lateral meniscus involving popl iteal hiatus, based on meniscal plasty, suture repair of the popl iteal hiatus would contribute to preserve the peripheral part and restore its stabil ity.