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Seniors around the World Want the Same Thing from Total Knee Replacement: A Knee That Bends

Senior citizens in the United States, Asia, and the Middle East agree on at least one thing. After having a knee joint replaced, they all know that bending the knee fully is the key to many, many daily activities. Getting a new knee joint isn't enough. Full knee flexion is also needed.

Researchers at the Biomotion Foundation in Palm Beach, Florida, are doing their part to help seniors with this problem. They studied 121 patients with 16 different types of joint replacements. Fluoroscopy, a special type of X-ray, was used to show the patients' knee motion on a TV screen.

The researchers found that there is more knee flexion when the thighbone (femur) rests more toward the back of the lower leg bone (the tibia). This position is called posterior femoral position.

The type of implant and its shape decide this position. Some implants allow the femur to move freely forward and back during knee flexion. Others push the femur forward during flexion. One implant forces the femur backward during knee flexion. This is the posterior-stabilized arthroplasty. The posterior-stabilized implant generally gives patients the most knee flexion.

The authors conclude that doctors' surgical skill and methods may not be the only factors in getting knee flexion back after a total knee joint replacement. It seems that the implant design is also linked to how much knee flexion patients gain.

References: Scott Banks, PhD, et al. Knee Motions During Maximum Flexion in Fixed and Mobile-Bearing Arthroplasties. In Clinical Orthopaedics and Related Research. May 2003. Vol. 410. Pp. 131-136.

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