Posterolateral corner (PLC) laxity of the knee results in rotatory instability, in association with posterior cruciate ligament (PCL) laxity led to a grossly unstable knee. This is a series of eight patients with chronic PLC and PCL laxity treated with arthroscopic quadriceps tendon PCL reconstruction and extraarticular hamstring PLC reconstruction. Seven cases had high tibial osteotomy to address associated genu varus deformity. With prospective pre- and post-operative assessments, there was a significant improvement in the 2000 International Knee Documentation Committee (IKDC) subjective assessment and knee examination, Lysholm-Gillquist and Tegner activity scores, as well as KT-1000 arthrometry measurement after one year in all knees. Surgical treatment of PLC laxity must address coexisting problems of the PCL and mechanical alignment for a successful outcome.