Knee Replacements

Knee replacement surgery is performed to correct or replace a knee joint which has become damaged or worn out. Knee replacement devices are artificial joints which are mostly manufactured by a few companies like Zimmer Biomet, Smith & Nephew, DePuy, and Stryker.

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knee replacement

The knee is one of the first joints to “wear out” in the human body.  This tendency has been complicated by environmental factors regarding our lives today.  Obesity and inflammatory diseases contribute to the need for knee replacement, that coupled with longer lifespans has led the development for knee replacement devices.  An estimated 700 thousand patients receive knee replacement surgery each year in the US and the number increases each year.  The American Academy of Orthopaedic Surgeons has estimated by the year 2030, that yearly knee replacement procedures may top 3.5 million.

Knee replacements involve the surgical removal of a malfunctioning knee joint and replacement with an artificial, engineered joint.  The procedure dates back over a century but was modernized in late 1968.  Today’s knee replacement recipient tends to be younger and more active, demanding advanced technology.

Knee replacements are required due to an injured joint or one that has simply “worn out”.  Conditions such as arthritis and developmental abnormalities may cause the need for a knee replacement, but injuries and acute medical conditions also contribute.  Knee replacement surgeries are recommended when pain and lack of mobility interferes with normal daily activities.

Knee replacement procedures can be done as a total knee replacement involves all three compartments, the medial compartment (inner knee), the lateral compartment (outer knee) and the patellofemoral compartment (front of the knee) where the entire joint is removed from the top of the larger lower leg bones (tibia) to the bottom of the top leg bone (femur).  Partial knee replacement will involve only one of the three compartments, generally the medial or lateral compartment.  The type of knee replacement surgery will vary from patient to patient based on the severity of joint degradation.

Knee replacements have improved the quality of life for millions of patients, however some patients ultimately experience more harm than benefit.  Like many other joint replacement procedures, knee replacements use medical devices that are frequently found to be defective resulting in complications that create severe adverse events and may require revision surgery.

Knee Replacement Components

Knee replacement devices are constructed of three different components. A total knee replacement will use a system that requires all of the components, where a partial knee replacement may use only one of two.

Femoral Component

a metal piece attaches to the end of the femur which has been removed. It is constructed with a center groove that allows the patellar component to slide freely as the knee is bent and straightened.

Tibial Component

a flat, metal and plastic (polyethylene) part is cemented or attached to the tibia. The metal portion sits atop the tibia and has a metal rod or stem that is inserted into the bone to stabililze it. The tibial spacer is made of a high density plastic and cushions the knee joint between the tibial component and the femur or femoral component.

Patellar component

covers the underside of the knee cap or patella. It is constructed of plastic and is shaped to match the patella. As it must be nestled and rest correctly within the joint, placement and alignment is critical, in order for the joint to function correctly.

Some knee replacement systems require the use of cement to stabilize the implants while other systems are designed to allow the bone to grow into the implant to provide stability. Cement-less procedures are used more often on younger patients but are more likely to become detached.

Knee Replacement Systems

There are several different types of knee replacement systems.  The patient and physician will work together to decide on a type of system that is best for the individual patient.

  • Fixed bearing knee replacement devices are best suited for patients who are not as active but are not overweight.  They are not as strong as some other implants and do not allow for as much mobility.  They have been used for a longer period of time than other systems.
  • Mobile bearing, rotating platform implants provide for some flexibility by allowing the tibial component plastic cushion to rotate.  This gives greater flexibility on the sides of the knee and is used in young and active patients.
  • Mobile bearing, medial pivot rotates and flexes like the natural knee joint.  Also used for younger, more active patients.
  • Posterior cruciate ligament retaining implant keeps the posterior cruciate ligament intact and is less invasive but not appropriate if ligament has been damaged.
  • Posterior cruciate ligament substituting implant replaces the ligament with a plastic component.  It is used for patients with damaged or weak ligaments and often used in revision surgeries.
  • Gender specific implants are designed for women whose physiology may differ from implant systems which are traditionally modeled on male anatomy.

Knee Replacement Complications

Despite the design of knee replacement systems intended to improve mobility and the quality of life in patients who receive them, many knee replacement implants have created serious adverse events.  In most of these patients, a knee implant revision surgery will be required which is much more costly and invasive.  Knee revision surgeries are more difficult to perform, may require extensive reconstruction, and may require a significantly longer period of recovery.

Knee replacement surgery complications can include mild or common effects such as:

  • Pain, bruising and swelling of the knee
  • Stiffness of the knee which may or may not resolve

More severe complications from knee replacement may include serious and possibly life-threatening effects such as:

  • Persistent or increasing knee pain
  • Infection with fever or chills
  • Blood clots creating pain in the lower leg
  • Nerve and blood vessel damage which may be permanent
  • Knee replacement failure resulting in dislocation and severe pain
  • Periprosthetic fractures in bone surrounding the implant
  • Particle shedding from device structure that is deposited into surrounding tissue
  • Osteolysis or necrosis (bone dissolution or tissue death) caused by shed particles

Knee Replacement Revision Surgery

A knee replacement procedure is designed to last for more than 20 years but up to 90 percent of patients will require a second surgery between 10 and 20 years after the original implant.  Nearly 70 thousand knee revision surgeries are performed each year and unfortunately some of those procedures are required within a few years of the original surgery.  This is considered an adverse event related to the implant itself.

Revision surgery carries a greater risk for the patient.  It is generally more complicated for the surgeon to perform and may require reconstructive procedures.  It is a more invasive and more costly procedure and typically requires a much longer period of recovery and rehabilitation.

Premature implant failure (within a few years of implant) has resulted in thousands of lawsuits filed against manufacturers of certain implant devices.

The FDA 510(k) Approval Pathway

Medical devices are classified by the Food and Drug Administration (FDA) into three categories.  Joint replacement devices, including knee replacement implants are in the Class III division which indicates significant risk to the patient.  Class III devices generally require a Premarket Approval (PMA) application in order to offer the device for use in the US.  The PMA process requires lengthy and costly clinical studies be performed in humans to prove efficacy and safety, however several knee replacement devices have been approved using a shorter pathway.

The FDA’s alternative pathway, known as 510(k) is generally used only for Class I and II devices.  An exemption is occasionally allowed for a Class III device if the manufacturer can claim that the device is substantially similar to and not substantially different from products that are already approved for use.

This pathway is intended for upgrades and minor manufacturing improvements, however the FDA has allowed several knee implant devices to be approved using this pathway.  This has meant that multiple devices have entered the US market without being subjected to clinical studies which would potentially have identified increased risk of adverse events.

Knee Implant Manufacturers

There are numerous companies who manufacture knee and other joint replacement devices.  Several of these manufacturers are facing thousands of lawsuits regarding high failure rates and other issues in their products.  In addition, four of the largest knee implant manufacturing companies settled with the US government in 2007 regarding claims that they paid surgeons to use their implants.  The manufacturers (Zimmer Holdings, DePuy Orthopaedics, Smith & Nephew, and Biomet) agreed to pay $310 million in penalties for the investigation.  Another manufacturer, Stryker Orthopaedics, agreed to 18 months of federal supervision instead of a fine.

Zimmer Holdings Inc.

Zimmer will be the second largest orthopedics company in the US after completion of its acquisition of Biomet.  Zimmer manufactures NexGen knee replacement devices.  Several of the NexGen device components have been recalled due to high incidence of failure. Another product, not part of the NexGen line, the Natural-Knee II Durasel Patella was originally manufactured by Sulzer Medica, acquired by Zimmer also faces a recall.

Products facing recall and lawsuits include:

  • NexGen MIS Tibial Components
  • NexGen TM Tibial Trays
  • NexGen LPS-Flex GSF Femoral Component
  • NexGen MIS Modular Tibial Plates and Keels
  • Natural-Knee II Durasel Patella

Zimmer Holdings recalled the MIS Tibial component in 2010 due to a locking mechanism failure.  Sulzer Medica had previously paid $1 billion to settle lawsuits regarding other implants. Zimmer is currently facing over one thousand lawsuits regarding failed knee implants.  Over 1000 of these lawsuits regarding the NexGen devices have been consolidated in multidistrict litigation (MDL) in the State of Illinois.

DePuy Orthopaedics

DePuy Orthopaedics – a division of Johnson & Johnson, the largest medical and pharmaceutical products company in the world, developed a range of High-Flex knee implants.  Several of the implant components have been recalled since 2008.  The FDA has also warned DePuy in 2010 regarding accusations of marketing without approval, though one of these systems was subsequently approved and others were removed from the market.

Products that have faced recall, penalties and lawsuits include:

  • TruMatch Personalized Solutions
  • PFC Sigma Knee System with titanium components
  • PFC Sigma Knee System components, sizes 2.5, 7 and 8
  • PFC Sigma Knee System 30mm – 40mm thick inserts
  • Femoral heads that include a 14/16 taper
  • Femoral heads with offsets greater than +12
  • LPS Diapyseal Sleeve
  • LCS Duofix Femoral Component

All of these DePuy products have faced FDA scrutiny, warnings, or recalls and DePuy faces multiple lawsuits regarding several products.

Smith & Nephew

Smith & Nephew has recalled several of its knee replacement devices due to higher than normal failure rates including inaccurate labelling issues regarding higher-than-specified iron contents in metal used for construction.

Products that have faced recall include:

  • Journey Uni Tibial Baseplate
  • Oxinium Genesis II and Profix II

At least three recalls regarding knee implant components have been made by Smith & Nephew since 2003.


Stryker has been forced to recall a number of products including knee replacement device systems, components and surgical aids.

Products that have faced recall and warnings include:

  • ShapeMatch Cutting Guide
  • Duracon Total Knee
  • Unicompartmental Knee System
  • Scorpio PS and CR components

Stryker has also received FDA warning letters regarding some products.


Biomet is set to be acquired by Zimmer Holdings in 2015 and will be part of the second largest orthopedics company in the US.

  • Vanguard PS Open Box Femoral Component
  • Vanguard DCM PS Plus Tibial Bearing Implant
  • Vanguard CR
  • Biomet Surgical instruments

Biomet has issued several recalls regarding its components and surgical supplies due to improper labelling and improper assembly.  The Vanguard CR system may be facing multiple lawsuits regarding implant failure.

Knee Replacement Recalls and Lawsuits

Many of the malfunctioning knee implants are still in the recall stage and full implications of implant failures have not come to light. Some companies are facing thousands of lawsuits, but some have yet to be filed.

Device companies who have manufactured knee implants that have been recalled or have shown defects can be held accountable for causing harm to patients. They may also be liable for additional damages if it can be shown that the manufacturer knew that a device was defective and continued to manufacture it anyway.

Often a patient who has received a device that is subject to recall will be contacted by the device manufacturer. Patients should speak to an attorney regarding their rights before giving any information to the manufacturer or their representative. Manufacturers who gather information may offer compensation but this will generally require that the injured patient waive rights to a lawsuit by accepting the offer.

A manufacturer may also try to collect information which may lower the financial compensation that would be required. Patients who have been injured or whose knee implant is subject to a recall, should speak with a licensed, experienced attorney before discussing any information with a manufacturer.

Notwithstanding claims relating to this product, the drug/medical device remains approved by the U.S. FDA. 

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