The arthritis pain in your knee is worse, and the exercise that once helped you feel better has become unbearable. Your doctor suggests a total knee replacement (TKR).

When you research the procedure, you discover there are gender-specific knees, which are knee replacement models designed for women, and dozens of other options, too – different materials, sizes and models from a variety of manufacturers.

How do you choose? Generally, you don’t. Surgeons typically determine which implant they’ll use when they are in the operating room and actually looking at the structure and size of your bones.

Prior to surgery, however, you should have an informed conversation with the doctor about your options so you can ask good questions about why a particular model might be chosen, and determine if you’re comfortable with the doctor’s approach and experience – or whether you’d like a second opinion.

Here are some key details.

Gender specific knees. “Knee implants were originally based on an average of shapes and sizes of both men and women,” explains Matthew J. Kraay, MD, professor of orthopaedic surgery at Case Western Reserve University School of Medicine in Cleveland. “Researchers then looked at the anatomy of women’s knees [and found] the biggest difference is that a woman’s knee is narrower.”

Makers of artificial knees then developed implants with this in mind – but that doesn’t necessarily mean they’re better for most women. After all, manufacturers produced a variety of knee-replacement sizes before gender-specific knees (GSK) came into the picture about five years ago.

In fact, there is no scientific evidence that a gender-specific knee improves surgery outcome – though it still might be the best choice for you because of fit. “The GSK gives surgeons more choices for a patient with a narrow knee. It is similar to shoes coming in both B and D widths,” says Dr. Kraay.

New materials. Each replacement knee is made up of three major parts. Typically, the femoral component is implanted in the large bone above the knee and is usually made of a highly polished, strong metal such as stainless steel, titanium or chrome and cobalt alloys.

The tibial component is placed in the bone below the knee and is made of a durable plastic held in a metal tray. The patellar component, also plastic, is attached to the underside of the kneecap.