When two surfaces rub against each other, the effect of that rubbing on either surface will depend on friction, wear and lubrication at the point of contact. For example, the femoral and tibial components of knee implants routinely rub against each other during daily activity such as walking or stair climbing. If the performance of the tibial component needs to be analyzed, the principles of contact mechanics and tribology are used to determine the wear performance of the implant and the lubrication effects of synovial fluid.