The present invention provides a tibial prosthetic knee component. The prosthesis includes a tibial tray having a posterior rail and an anterior rail, and a tibial insert. The tibial insert has a posterior dovetailed surface matching the posterior rail in the tibial tray, and an anterior surface matching the anterior rail in the tibial tray. The posterior rail of the tibial tray and the posterior dovetailed surface of the tibial insert are curved to provide clearance for the posterior cruciate ligament. A retaining clip is provided for retaining the tibial insert in the tibial tray. The clip includes a tab which extends through the tray into the insert and a resilient holding member remains unloaded when loads are applied to the knee, reducing the likelihood of dissociation of the tray and insert.