What you need to know about patellofemoral replacement
Patellofemoral replacement is a type of partial knee replacement surgery that can be an option instead of total knee replacement. Dr Dan Fick explains some key facts about this relatively new type of orthopaedic procedure.
Patellofemoral replacement, also known as kneecap replacement or patellofemoral arthroplasty, is a type of partial knee replacement surgery that is relatively new compared to traditional total knee replacement surgery.
A key aim of the surgery is to relieve knee pain that may be caused when your protective cartilage wears out (usually due to arthritis), causing the damaged surface of your kneecap to grind against your thighbone (femur). Patellofemoral knee replacement surgery replaces the damaged portion of your knee joint under your kneecap and the adjacent part of the thighbone with a new artificial joint.
The healthy cartilage and bone, as well as all of the ligaments in the rest of the knee, are preserved.
The patellofemoral joint is where the back of the kneecap (patella) meets your thighbone (femur) at the front of the knee.
Who needs this type of surgery?
Patellofemoral replacement may be a good option for you if you have arthritis in your patellofemoral joint (where the back of your kneecap joins the thighbone at the front of your knee), but the rest of your knee is healthy.
The patellofemoral joint is involved in climbing, walking on an incline, and several other knee movements, and is the joint most commonly affected when you have “runner’s knee”, with pain, rubbing, grinding, or clicking of the kneecap.
This is not your best option if you have:
- knee stiffness
- ligament damage
- poor patellar (kneecap) tracking
- a major deformity of the leg
- inflammatory arthritis, such as rheumatoid arthritis
- crystalline arthritis, such as gout.
What happens during patellofemoral replacement surgery?
In patellofemoral replacement (right), the healthy parts of the knee are kept, while in total knee replacement (left), the entire joint is removed and replaced with a prosthesis.
You will need either general anaesthetic or spinal anaesthesia to have this surgery – we will discuss which option is right for you prior to your procedure.
During this procedure, I’ll make a surgical incision at the front of the knee to resurface the underside of the kneecap and the trochlear groove (the groove on the thighbone that holds the kneecap).
First, I’ll remove the damaged cartilage and a small amount of bone from the patellofemoral compartment of your knee. Then I’ll use a plastic cover, or button, to resurface the underside of the kneecap. This button will line up with a thin metal component that is used to resurface the trochlear groove at the end of the thighbone.
The healthy cartilage and bone, as well as all of the ligaments in the rest of the knee, are preserved. The skin incision is usually closed with staples. The surgery takes about 1.5 hours to complete.
If I find damaged cartilage outside of the patellofemoral compartment, there is a chance that I may have to do a total knee replacement instead, but we will have discussed this possibility well before your surgery.
Patellofemoral replacement vs total knee replacement surgery
It’s a smaller surgery than total knee replacement
This means less blood loss, a smaller surgical incision, less pain and swelling and reduced risk of complications during and after surgery.
Shorter hospital stay
Because it’s a smaller procedure than total knee replacement surgery, you’re likely to be discharged from hospital quicker. Your stay in hospital may be 2–4 nights after patellofemoral replacement surgery.
A key advantage over a total knee replacement is that the knee will have a much more natural feel to it. This is because all the ligaments in the knee are preserved along with rest of normal articular cartilage.
Recovery from this surgery is a little quicker than total knee replacement surgery so you can get back to normal activities sooner.
Potential disadvantages of
You may need future surgery
The main disadvantage of patellofemoral replacement compared with total knee replacement is that you may need more surgery in the future. For example, if arthritis develops in a part of the knee that we haven’t replaced, you may need total knee replacement surgery to help fix it.
We will aim to start physiotherapy on the day of, or the day after, your surgery, but expect to use crutches for a few days or weeks. You should be able to walk independently and use the bathroom independently after a few days.
You’ll experience some pain and stiffness in the first few weeks after surgery – that’s normal.
If you could walk without an aid prior to the surgery, you should be able to get back to normal in less than 3 months and within 12 months, you should be fully recovered and living an active life without knee pain.