Irreducible knee dislocation is a rare injury and often need an open procedure with ligaments reconstruction. This report describes a case of arthroscopic treatment of a patient with traumatic knee dislocation unable to reduce in a closed method. MRI revealed incarceration of the medial collateral ligament and capsule in the medial compartment. And arthroscopic examination confirmed incarcerated medial capsuloligamentous structures which prevented the knee from reduction. Arthroscopic procedure without ligaments reconstruction was complete when the medial condyle was well visualized and the knee reduced. After 4 weeks of immobilization in extension, range of motion exercise and gradual increases in weight bearing was allowed. At the 3- year follow-up, mild laxity was remained but the patient did not have any discomfort of doing ADL activity and showed full range of motion of the knee.