Patellofemoral Surgery and Replacement

A New and Better Way to Restore Knee Function and Relieve the Pain of Kneecap Arthritis and Wear


Pain and loss of function from kneecap (patella) arthritis and cartilage wear is a common problem afflicting up to 10 percent of the population. Patients often undergo multiple operations only to end up with severe disability. This is because many of the traditional solutions have been shown to have fairly high failure rates, averaging 30 percent (Table 1). Establishing the correct cause of kneecap pain, knowing when to perform an operation and, as important, knowing when not to perform an operation, are critical to successful treatment.

Knee painTable 1. Operative approaches for patellofemoral arthritis

  • Arthroscopic debridement
  • Microfracture articular restoration
  • Lateral release
  • Soft-tissue realignment of the extensor mechanism
  • Osteotomies of the tibial tubercle
  • Mosiacplasty/autologous chondrocyte implantation
  • Lateral patella partial facetectomy
  • Patellectomy (removal of the kneecap)
  • Total knee replacement

Arthritis of the Kneecap

Articular cartilage is the tissue covering the ends of bones where they meet to form a joint (think of the knuckle of a chicken drumstick). That precious layer must remain intact, smooth and of a proper thickness, or your body weight will not be cushioned and the bending of the joint will feel rough with increased mechanical friction.

Degenerative arthritis (also known as osteoarthritis) is the type of knee arthritis resulting from accumulative wear and tear or direct trauma damage to that joint surface. Kneecap cartilage damage is also called chondromalacia patella (chondro = cartilage, malacia = softening, patella = kneecap). Whatever the reason, once the joint surface deteriorates, the underlying bone is exposed and pain increases due to the overloading of the many underlying nerves.

If the joint surface cannot be fixed or repaired, the force of the joint must be reduced or the surface artificially protected (replacement).

Indications for Patellofemoral Replacement

The indications for patellofemoral replacement are summarized in Table 2. While operative replacement of any portion of the knee joint is one of the last options, it is often the only remaining choice when other treatments fail or result in increased pain. We have found a definite trend of more rapid recovery, better function, more predictable return to work and decreased dependency on pain medication with this operation. Patients can become very depressed and socially drained by the stress of constant pain and ineffectual prior treatment. Patellofemoral replacement offers more predictable relief from these problems.

Table 2. Indications for Patellofemoral Replacement

  • Degenerative osteoarthritis (i.e., loss of joint space with osseous deformation) limited to the patellofemoral joint
  • Severe symptoms affecting daily activity referrable to patellofemoral joint degeneration unresponsive to lengthy (three to six months) nonsurgical options and/or failed prior conservative procedures (e.g., lateral release, arthroscopic debridement, cartilage transplantation)
  • Post-traumatic osteoarthritis
  • Extensive Grade 3 chondrosis (i.e., loss of joint space without osseous deformation of the patellofemoral, joint space, particularly pantrochlear, medial facet or proximal half of patella)
  • Failed extensor unloading procedure (e.g., Maquet, Fulkerson)
  • Patellofemoral malalignment/dysplasia-induced degeneration, with or without instability

Contraindications to Patellofemoral Replacement Surgery

Some patients cannot have this operation either because their knee is too damaged or they have one of the conditions listed in Table 3.

However, most patients should consider this procedure as a possible option for their patella arthritis and get evaluated before choosing a treatment. It is important to seek a surgeon who has experience with patellofemoral replacement, since opinions vary greatly depending upon the individual surgeon's own preferences.

Table 3. Contraindications to Patellofemoral Arthroplasty

  • No attempt at nonoperative care or to rule out other sources of pain
  • Arthritis involving the tibiofemoral articulation greater than Kellgren Grade 1/2
  • Systemic inflammatory arthropathy
  • Osteoarthritis/chondrosis less than Grade 3/4
  • Patella infera
  • Uncorrected patellofemoral instability/malalignment
  • Uncorrected tibiofemoral mechanical malalignment (valgus>80; varus >50)
  • Active infection
  • Evidence of chronic regional pain syndrome
  • Fixed knee range of motion loss (-100 ext. -1100 flex. minimum)
  • Psychogenic pain

Table 4. Additional Factors That May Adversely Affect Patellofemoral Arthroplasty Outcome

  • Multiple antecedent procedures or extensive soft-tissue trauma associated with residual quadriceps atrophy
  • History of prior arthrofibrosis in the same joint or other operative site
  • Ligamentous tibiofemoral instability
  • A post-menisectomy knee
  • Chondrocalcinosis
  • High patient activity or bent knee use
  • Age under 40
  • Unrealistic patient expectations
  • A surgeon with lack of experience in arthroplasty or extensor mechanism realignment
  • Obesity (BMI >30)
  • Patella alta
  • Primary osteoarthritis
  • Male gender

Treatment Options

Patients are often told that there is nothing more that can be done for them and they must live with the pain, or worse, accept a much larger and potentially complicated total knee procedure. Many patients are younger than 50, and to live with the pain and disability of kneecap arthritis is not an option. These patients are very intimidated by the choices offered to them, especially if their surgeon offers no solution. Fortunately, our experience and the overall technological progress with patellofemoral replacement now provides a better answer.

Patellofemoral Replacement: Patellofemoral replacement, often called kneecap replacement or patellofemoral arthroplasty, is one type of minimally invasive knee surgery. The parts are very small compared to a standard total knee replacement.

Standard Total Knee Replacement: The greater size of the components means a larger portion of the normal knee is sacrificed with greater operative risks and a less natural-feeling function. If a total knee operation fails or you experience a complication, the solutions in most cases are more complicated than with a patellofemoral replacement.

Steps to Take

At the Rubin Institute's Joint Center for Preservation and Replacement, patients come from across the United States and the world to seek additional opinions. To get the most out of your visit and achieve proper treatment, you must do the following:

  • Request a copy of your operative reports and medical records from your previous physician.
  • Bring copies of any X-rays or MRIs
  • Write a concise history of your problem and treatment.
  • Contact us at 410-601-BONE (2663) or visit our website.