Arthritis Health Center

Knee, Hip Replacements Carry Blood Clot Risk

Risk of Blood Clots ‘Extends Beyond the Hospital Stay’ continued...

"They are missing a lot of people who have clots," he says.

Their estimates may be on target for just the hospitalization period, he says. However, because the risk for clots persists much longer, depending on the surgery, the estimates of overall clot risk may be off, he says.

Citing several published studies, Heit says the risk period for clots in the deep veins, for instance, can be up to 12 weeks after hip replacement and up to six weeks after knee surgery.

These long-term risks are the most important for patients to know about, he says.

About 80% of the patients in the studies analyzed were in clinical trials, he says, noting that those patients may differ in important ways from other patients.

"The real risk extends beyond the hospital stay," says Bert Thomas, MD, attending surgeon and chief of the joint replacement service at Santa Monica-UCLA Medical Center & Orthopaedic Hospital. He is also a professor and division chief of the joint replacement service at the University of California Los Angeles David Geffen School of Medicine.

"So we recommend preventive anti-clotting medicine continue for six weeks," Thomas tells WebMD.  "Some doctors think it should go longer."

However, he says, the anti-clotting medicines themselves carry risks, such as bleeding.

Risk of Blood Clots: What Patients Can Do

Patients can take steps to reduce the blood clot risk, Heit and Thomas say. Among the ways:

• Stop smoking. "Smoking boosts the risk of getting blood clots," Thomas says.
• Lead an active lifestyle as much as possible.
• Lose weight before surgery if necessary.

Thomas reports consulting work for Smith & Nephew, which makes orthopaedic products, and Consensus Orthopedics. Heit reports serving on advisory boards for Daiichi Sankyo, GTC, and Ortho-McNeil-Janssen.