Knee Arthritis: Patellofemoral Joint (Kneecap) Replacement Animation

Knee Arthritis: Patellofemoral Joint (Kneecap) Replacement Animation

This animation demonstrates a patellofemoral joint arthroplasty, also known as a kneecap replacement, for the treatment of knee arthritis. Here, we see a right knee joint consisting of the thigh bone, or femur, patella, or kneecap, and tibia, or shinbone.

An incision will be made along the front of the knee. The knee is bent, and the kneecap is flipped over to expose the underside surface. The cartilage and damaged bone on the underside of the kneecap are first shaved down. Three holes are drilled into the exposed surface of the kneecap to prepare the bone for a plastic implant.

A guide is then inserted over the end of the thigh bone, and a drill is inserted through the hole of the guide to make a hole in the bottom of the thigh bone. The guide is removed, and a sizing base is inserted into the drilled hole. A metal pin is placed through the base on one side of the knee to hold it in place. A cutting guide is attached to the base and used to determine the correct level of bone to be removed.

A bone saw is inserted through the guide and used to remove the top section of the front of the thigh bone that contacts the kneecap. Next, the guide and instruments are removed, and another sizing guide is placed over the end of the thigh bone. The guide is held in place with metal pins, and a reamer is inserted through the openings in the guide to remove more bone from the thigh bone.

A chisel-like instrument called an osteotome is then inserted into the slits of the guide to help remove the remaining bone. The pins and guide are removed. A trial implant is placed on top of the thigh bone and held in place with metal pins. Then, 3 holes are drilled into the thigh bone through the implant. The pins and trial implant are removed, and a final metal implant, coated with bone cement, is placed on top of the bone.

The plastic implant for the kneecap is also coated in bone cement and secured to the prepared surface of the kneecap. The kneecap is flipped over and aligned back in place. The skin incision will be closed with sutures and the kneecap replacement is complete.