Scientists Develop 3-D Knee Model for Predicting Joint Stress

Scientists at Anglia Ruskin University in the United Kingdom have developed a 3-D model to predict knee stress, based on validated force and movement data, to help osteoarthritis patients delay the need for full knee replacement surgery and potentially save the National Health Service (NHS) significant money annually.

Working alongside colleagues in New York, experts at Anglia Ruskin’s Medical Engineering Research Group have built a model to predict pressure in the knee joint following less intrusive surgical reconstruction procedures.

Osteoarthritis is a debilitating disease that often leads to pain and disability in the elderly. About 14 percent of men and 23 percent of women over 45 years of age show signs of knee osteoarthritis and the NHS performs over 70,000 knee replacements each year in England and Wales.

“There is no cure for osteoarthritis and joint replacement is often the ultimate solution. Total knee replacement is expensive, involves the removal of ligaments and alters the knee function,” Dr. Rajshree Mootanah, director of Anglia Ruskin’s Medical Engineering Research Group, said. “It is important to treat knee osteoarthritis early to preserve the natural joint tissues. This model can help surgeons with that procedure.”

To create the computerized model, high-resolution magnetic resonance images of a 50-year-old cadaveric knee were obtained at the Hospital for Special Surgery in New York. The relevant tissues were segmented by scientists at Anglia Ruskin to create an accurate 3-D representation of the knee joint. The university claims the 3-D model is the first of its kind in the world.

Material properties of the tissues then were allocated to the bones, cartilage, meniscus and ligaments. The cadaveric knee was fixed on a six-degree-of-freedom robot, controlled loading was applied and knee joint pressures were measured.

Following a special technique, called the ligament tuning process, the material properties of each ligament were obtained at every position of the knee joint. The same loading conditions, applied on the cadaveric knee, were simulated in the knee model and joint pressures were predicted.

The experimentally-measured and computer-simulated knee pressures were compared to validate the knee model.