Phys Ed: What Causes Early Arthritis in Knees?

By GRETCHEN REYNOLDS
NYT

Recently, Dr. Constance R. Chu, the Albert Ferguson associate professor of orthopedic surgery at the University of Pittsburgh and director of the Cartilage Restoration Center there, confirmed a theory, and found herself troubled by the results. It turned out that if you dropped a heavy weight onto parts of a cow’s knee joint from various heights, the joint was hurt. (While the parts of the joint were damaged, the cow itself was uninjured by the experiment; the knees came from a local abattoir.) When the weight hit the joint’s surface cartilage with great speed and force, the bone and cartilage fractured. No surprise there. But it is what happened in Dr. Chu’s experiment when the impact was more subtle — closer to, for instance, the perturbations inside a human knee when a ligament is torn — that concerned her. She found that with lighter impact, the various parts of the knee appeared, visually at least, to be fine.
Phys Ed

But when Dr. Chu and her colleagues examined the cartilage cells just below the placid surface, they found carnage. “Many of the cells within the impact zone” — the area that had been directly thwacked by the weight — “were dead,” she said. They died instantly. More insidiously, other cartilage cells, those outside the injury site, began to die in the hours and days after the impact. “We saw an expanding zone of death,” Dr. Chu said. By the end of her group’s planned observation period, four days after the impact, cartilage cells well away from the original injury site were still dying.

(Continued here.)