The wear of polyethylene cup in hip and knee implants is influenced by a set of primary parameters, has been reported to lead to loosening of the implant and osteolysis. Mass loss as a result of wear and osteolysis may cause dislocation and subsequently revision and/or replacement of the implant. An attempt was made to develop, in the case of hip implant, a comprehensive wear rate equation in terms of the implant dimensions namely, femoral head roughness, femoral head diameter, subject body weight and mechanical properties of ultra high molecular weight polyethylene (UHMWPE). The effect of mechanical properties of polyethylene was included into the model and that resulted in more comprehensive equation. In the case of knee implant an attempt was made to develop in vitro wear rate model in terms of the experimental parameters, such as load and traveled distance.