Due to the high incidence of deep venous thrombosis (DVT) following orthopaedic surgery, DVT prophylaxis is imperative. Because of the morbidity associated with these complications, it is essential to provide prophylaxis for DVT as well as pulmonary embolism. Currently there are various prophylactic modalities available to the clinician, involving both chemical and mechanical forms of treatment. Unlike, current forms of chemoprophylaxis, which are not without their associated side effects and costs, mechanical treatments have been shown to be both safe and effective. Previous studies have shown mechanical compression devices to be efficacious in reducing the rate of DVT after orthopaedic surgery. These compression devices vary according to the location of the sleeve and bladder, frequency and duration of activation rate, rate of pressure rise, maximum pressure achieved, and simultaneous versus sequential compression. Moreover, pneumatic compression devices are further categorized as foot pumps and calf-thigh pumps, of which some are single chamber whereas others are sequential chambers with a number of compartments. This chapter discusses the specifications of the mechanical devices in relation to their clinical efficacy as well as the effects on venous hemodynamics and physiology.