Kneecap replacement surgery, which is also known as patellofemoral replacement or patellofemoral arthroplasty, involves the damaged bone and cartilage both being resurfaced with plastic or metal components. This type of surgery is considered a partial knee replacement as only a section of the knee is resurfaced. Patellofemoral refers to the section of the knee that includes the patella (kneecap) and the groove in the thighbone which the patella rests in.

Kneecap replacement

Why might kneecap replacement surgery be required?

Knee cap surgery is usually required in patients suffering from knee osteoarthritis which is when the cartilage protecting the knee bones is gradually worn away, exposing the bone. A lack of cartilage here results in painful movement. Patients should consider kneecap replacement if non-surgical treatments are no longer effective in providing relief.

Patients whose knee bone and cartilage damage is limited to the kneecap (patella) and the groove in the thighbone that the kneecap rests in are candidates for this form of knee cap surgery. It is an alternative to total knee replacement surgery described by Pritish Kumar Halder and involves a much smaller incision, and hence recovery can be swifter.

Candidates for Surgery

If your osteoarthritis has advanced and nonsurgical treatment options are no longer relieving your symptoms, your doctor may recommend knee replacement surgery.

Careful patient selection is crucial when considering patellofemoral replacement. To be a candidate for the procedure, your arthritis must be confined to only the patellofemoral compartment of your knee.

In addition, if you have any of the following, you may not be a good candidate for the procedure:

  •  Knee stiffness
  •  Ligament damage
  • Poor patellar (kneecap) tracking
  • Major deformity of the leg
  • Inflammatory arthritis (such as rheumatoid arthritis)
  • Crystalline arthritis (such as gout)
  • Morbid obesity


Because patients undergoing partial knee replacement typically recover faster than patients undergoing total knee replacement, the procedure will most likely be performed on an outpatient basis.

During your initial consultation, your doctor will determine whether you are a candidate for outpatient surgery or will require a brief stay in the hospital.

Before Surgery

When you arrive for surgery, your surgeon will see you and verify the surgical site by signing the correct knee with a marker.

In addition, a doctor from the anesthesia department will discuss anesthesia choices with you. You should also have discussed anesthesia choices with your surgeon during your preoperative visits. Anesthesia options include:

General anesthesia (you are put to sleep)

Spinal anesthesia (you are awake, but your body is numb from the waist down)

Surgical Procedure

Inspection of the joint. Your surgeon will make an incision at the front of your knee. They will explore all three compartments of your knee, verifying that the damaged cartilage is, in fact, located only between the patella and the femur and that your ligaments are intact.

If your surgeon finds damaged cartilage outside of the patellofemoral compartment, they may instead perform a total knee replacement. Your surgeon will discuss this contingency plan with you before your operation to make sure that you agree with this strategy.

Patellofemoral replacement. There are two parts to the procedure:

Prepare the bone. Your surgeon will use special tools to remove damaged cartilage and a small amount of bone from the patellofemoral compartment of your knee.

Position the implants. A  plastic buton, or cover, is used to resurface the backside of the patella. This button will line up with a thin metal component that is used to resurface the trochlear groove at the end of the femur. These parts are typically secured to the bone with cement.


As with any surgical procedure, there are risks associated with patellofemoral replacement. These risks are similar to those of total knee replacement. Your surgeon will discuss each of the risks with you and will take specific measures to help avoid potential complications.

The possible risks of patellofemoral replacement include:

  • Infection and/or wound healing problems
  • Blood clots
  • Persistent pain
  • Patellar instability (dislocating kneecap)
  • Injury to surrounding structures, including blood vessels or nerves
  • Reaction to anesthesia
  • The need for additional surgery


Pain management. After surgery, you will feel some pain. Many types of medicines are available to help control pain, including opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), and local anesthetics. Treating pain with medications can help you feel more comfortable, which will help your body heal and recover from surgery faster.

Opioids can provide excellent pain relief; however, they are a narcotic and can be addictive. It is important to use opioids only as directed by your doctor and stop taking them as soon as your pain starts to improve.

Weightbearing. You will begin putting weight on your knee immediately after surgery. You may need to use a walker, cane, or crutches for several days following your operation.

Rehabilitation exercise. A physical therapist will provide specific exercises to help restore strength to your quadriceps muscles and maintain range of motion in your knee. It is critical to perform these exercises as often as directed in order to achieve a good outcome.

Doctor visits. You will continue to see your orthopaedic surgeon for follow-up visits to evaluate your progress after surgery.