ObjectiveTo explore the technique of arthroscopic resection of benign tumor in the knee posterior septum and to evaluate its clinical results. MethodsBetween June 2008 and June 2012, 12 cases of benign tumor in the knee posterior septum were treated by arthroscopic surgery. There were 8 males and 4 females with an average age of 36.5 years (range, 22-50 years). The average disease duration was 8.4 months (range, 3 months to 2 years). Of 12 cases, there were 2 cases of chronic synovitis, 5 cases of ganglion, 4 cases of tenosynovial giant cell tumor, and 1 case of synovial hemangioma; solitary tumor involved in the knee posterior septum in 10 cases, and in the posterior septum and other part of the knee in 2 cases. All the patients underwent tumor removal under arthroscope with routine anterolateral and anteromedial portal, additional posteromedial portal and/or posterolateral portal. Trans-septal approach was used in 6 cases because the tumors located in the middle of the posterior septum. ResultsAll wounds healed by first intention with no complications such as infection, haematoma in the knee, injury of vessels and nerves, deep vein thrombosis, osteofascial compartment syndrome, or cutaneous necrosis. All patients were followed up 12-46 months with an average of 18.5 months. All patients achieved relief of knee pain and improvement of knee movement. The range of motion of the knee was significantly improved from (57.08±12.52)° at pre-operation to (120.83±13.95)° at last follow-up (t=-12.84, P=0.00). The visual analogue scale (VAS) score was significantly reduced from 5.00±1.04 at pre-operation to 1.50±0.91 at last follow-up (t=-18.00, P=0.00). The Lysholm score was significantly improved from 49.50±9.07 at pre-operation to 84.58±6.82 at last follow-up (t=-8.04, P=0.00). ConclusionThe benign tumor in the knee posterior septum can be completely resected under arthroscope, and the procedure is minimally invasive and useful to the restore knee function.