Standard vs Gender-Specific Knee Replacements in Women

June 14, 2018

Knee replacement surgery is considered among the best treatments for end-stage arthritis of the knee. A successful knee replacement relieves pain and restores near-full range of motion to a severely damaged knee.

When performing a total knee replacement, the surgeon must reproduce their patient’s anatomy as closely as possible. Because the anatomy of men and women’s knees vary quite a lot, it has led to the creation of gender-specific knee prosthetics. The goal of these new gender-specific prosthetics is to match the patient’s anatomy as closely as possible and minimize the risk of any complications.

However, the use of gender-specific knee replacements is still relatively new and there is no definitive answer if these types of prosthetics are more suitable than traditional replacements.

This article will provide information on the potential benefits and harms of gender-specific knee replacements.

The Differences Between Male and Female Knees

Gender-specific knee implants were developed in order to accommodate the natural anatomical differences between men and women’s knees. These differences include:

Q Angle

Q angle is the measurement of the angle between the quadriceps muscles and the patella tendon. It determines whether your knees are normal, pushed inwards, or pushed outwards.

A popular argument for gender-specific knee replacements is that men and women typically have different Q angles; however, some research has shown that this difference has been overstated in the past. In fact, some researchers theorize that the difference in angle has more to do with height than sex.

Femoral Condylar Height

The femoral condyles are the two round projections at the bottom of the femur. In the past, it was theorized that women had shorter femoral condylars than men. While research has disproven this theory, studies have confirmed that women and men have a different ML:AP aspect ratio.

ML:AP aspect ratio, also called the distal femoral aspect ratio and anteroposterior dimension, refers to the dimensions of the bottom of the femur where it connects to the knee. Gender-specific prosthetics take into account the difference in ML:AP aspect ratio between men and women, providing various fits to accommodate these differences.

Arguments for Gender-Specific Knee Replacements

Many knee replacements in women “overhang” the bottom of the femur by around 3 millimeters. According to a study published in The Journal of Bone & Joint Surgery, this overhang “doubles the odds of clinically important knee pain two years after total knee arthroplasty.”

Due to the difference in ML:AP aspect ratio between genders, some physicians theorize that standard knee replacements in women overfill the patellofemoral compartment (the divot at the bottom of the femur where the kneecap sits) and cause knee pain through soft tissue irritation. Prosthetic knees designed for this difference in ML:AP aspect ratio can better accommodate female knee anatomy and remove the overhang that has been shown to cause pain. However, at this time, there is no conclusive data to support this theory.

Arguments Against Gender-Specific Knee Replacements

Multiple peer-reviewed studies have shown that there is no significant difference in the longevity and function of gender-specific knee prosthetics compared to traditional knee prosthetics.

Moreover, an article published in Knee Surgery & Related Research specifically states that while gender-specific knee replacements do reduce femoral overhang, that reduction does not provide any measurable benefits 3-4 years after surgery.

Studies have also shown that height is a much better predictor of knee anatomy than gender. In other words, using gender as the basis for categorizing knee replacements has the potential to be extremely misleading. Also, some doctors are concerned that if knee prosthetics become gendered, men or women could reject the proper sizing for them because it was meant for the opposite sex. For example, a man may opt for a male-intended prosthetic despite a female-intended one being a better fit.

Trust Beacon for Your Knee Replacement

While it is not clear if gender-specific knee prosthetics provide improve a patient’s outcomes, the skill of the surgeon remains the most important predictor of knee replacement success. Choose a surgeon who is fellowship trained, meaning they have expertise in a particular type of joint replacement.

Dr. Haleem Chaudhary at Beacon Orthopaedics and Sports Medicine is fellowship trained in joint reconstruction from the Anderson Orthopaedic Research Institute in Alexandria, Virginia. In addition, he specializes in both full and unicondylar knee replacements. If you believe a knee replacement would be right for you, schedule an appointment with Dr. Chaudhary today.