Human bite wounds around the knee are rarely seen, yet may require the same urgent attention as a fight bite to the hand. Two cases of polymicrobial septic arthritis of the knee secondary to a human bite wound are described. In both the cases, the diagnosis of the septic arthritis was delayed because the intra-articular wound was unrecognized. The injuries were initially deemed superficial and managed with local wound care. In each case, the knee was flexed at the time of injury and the quadriceps tendon was penetrated by a tooth which inoculated the knee joint. Septic arthritis of the knee presented, in both cases, 72 hours after the injury. These infections proved challenging to treat and required multiple surgeries and prolonged antibiotic therapy. The “fight bite” phenomenon of the hand is widely recognized and the same phenomenon can occur at the knee.