The treatment of posterior malleolus fractures has traditionally been based on the size of the fracture fragment. Biomechanical evidence does suggest that larger posterior malleolar fragments can alter the load transmission through the tibiotalar joint. In trimalleolar fractures with smaller posterior malleolus fractures, fixation of the posterior malleolar fragment has been suggested as an alternative to the gold standard practice of fixing the fibular fracture first, then stressing the syndesmosis and adding transsyndesmotic fixation if necessary. This paper reviews the rationale for posterior malleolus fracture fixation based on fragment size and based on syndesmotic instability. The technique of posterior malleolar fixation is also reviewed.