Total knee arthroplasty is one of the most commonly performed orthopedic surgical procedures in the United States. It is the end stage treatment option for an arthritic knee that has failed all conservative management options. Primary concepts in the surgical technique include restoring limb alignment and soft-tissue balance about the knee. The overall goal is to decrease pain and improve function, ultimately improving a patient’s quality of life. Currently, traditional mechanical alignment concepts that focus on restoring neutral limb alignment have been challenged by the principle of kinematic alignment. In addition to these recent philosophical challenges, new technologies have been introduced to help the surgeon more accurately achieve optimal limb alignment and soft-tissue balance, aiming to improve patient outcomes following the surgery.

Introduction

A total knee arthroplasty (TKA) or total knee replacement (TKR) is indicated for those with end-stage osteoarthritis of the knee affecting 2 or 3 compartments of the joint. If only one compartment is affected, a uni-compartmental arthroplasty might be an option. A total knee replacement is considered once all other conservative options have failed. Those conservative options being weight loss, activity modification, use of oral NSAIDS such as ibuprofen or prescription Meloxicam, injections such as steroid, Hyaluronic Acid, or biologic injections (PRP or BMAC). Once all conservative options have failed and quality of daily living has deteriorated, it may be time to discuss the next step of a total knee replacement.

History

Total knee replacements began around the 1800s when the components implanted were composed of ivory. A special resin along with plaster of Paris were utilized to help fix these ivory components to the bone. Metal implants were introduced in the 1930s and then in the 1950s, the hinged knee construct was constructed to help replace the femur, tibia, and the collateral ligaments around the knee. These newer components showed acceptable results, however there was a high rate of failure along with poor long-term outcomes due to normal knee kinematics not being restored. In the 1970s, the components changed to mimic the natural anatomy of the distal femur while retaining the collateral and cruciate ligaments within the knee. The tibial component in the 1970s utilized a plastic bearing that allowed for flexion and extension of the joint. Building off this innovative construct from the 1970s, we now have advanced implants utilized in total knee replacement surgery that allow us to mimic the native anatomy as well as correct the kinematic alignment of the knee to help increase longevity and produce highly favorable outcomes.

Indications

A total knee replacement is an excellent option for patients who have end-stage osteoarthritis (grade 3 or 4) and have failed prior conservative treatment options (ex. injections, weight loss, physical therapy, bracing, etc). The procedure provides relief from pain and can restore normal daily functions with no limitations. The total knee replacement can also address malalignment that has occurred due to the progression of osteoarthritis. The most common alignment seen with knee osteoarthritis is the varus deformity, which is also known as being bow-legged. This deformity is a result of the loss of cartilage along the medial compartment of the knee which leads to the knee “bending” outward. The other alignment issue that can be seen with osteoarthritis is a valgus deformity or “knock knees.” This valgus deformity is not as common as the varus deformity and is caused by a hypoplastic (mal-developed) lateral femoral condyle, aggravated by loss of cartilage within the lateral compartment.

Clinical symptoms of osteoarthritis that would warrant a TKA include persistent pain with daily activities coupled with decreased range of motion. Additionally, you may experience worsening stiffness within the joint when initially getting up from a seated position. The patient may experience pain along either the medial or lateral aspect of the knee depending on where the predominant amount of arthritis is located. Physical examination will reveal decreased range of motion within the affected joint with tenderness along the medial or lateral joint line on palpation. Initial management would include conservative care such as weight loss, activity modification, use of oral NSAIDs such as ibuprofen or prescription Meloxicam, injections such as steroid, Hyaluronic Acid, or biologic agents including platelet-rich plasma (PRP) and bone marrow aspirate concentrate (BMAC, or bone marrow stem cells). Once all conservative management options have been exhausted and quality of life is declining, it may be time to consider a knee replacement procedure.