Blocking sensation from the femoral nerve by injecting local anesthetic around the nerve plays an important role in pain control after total knee replacement. However, femoral nerve block has been associated with increased risk of falls due to weakness of the thigh muscle. This prospective, randomized controlled trial asks the question whether blocking the more distal branch of the femoral nerve (saphenous nerve) will result in less muscle motor block, and thus less risk of falls. The study also aims to compare pain control after both techniques.