Overweight knee-replacement patients have more endothelial microparticles (EMPs) floating around their veins than other patients, according to a study published March 4, 2015, in the Journal of Bone and Joint Surgery. In addition, overweight patients have fewer helpful blood-vessel stem cells. These findings paint a picture consistent with other research showing heavier patients have more complications with knee replacement. The research findings also point to why.

EMPs are tiny packets released by stressed-out or dying blood-vessel cells that can upset the normal body balance needed to create new blood vessels. EMPs are an indicator of vascular health. The more of them there are, the worse the status of the vessels. They occur in larger quantities in patients suffering from such diseases as hypertension and type-2 diabetes.

The recent study looked at 74 patients who underwent total knee-replacement surgery. Researchers measured blood samples before surgery, directly after surgery, and three days post-surgery. The researchers also quantified the “good” endothelial progenitor cells (EPCs), which are stem cells that form blood vessels. At the three-day mark, obese patients had more EMPs and fewer EPCs than the patients of normal weight.

Knee replacement is an aggressive operation in which the joint affected by osteoarthritis is amputated, and then a prosthesis is forcefully inserted with mallets. It’s not surprising that there’s a storm of blood-vessel injury byproducts such as EMPs (bad) and EPCs (good). What’s interesting is that obese patients don’t handle this severe trauma as well as other patients, producing more bad EMPs and fewer good EPCs.

“Overweight Knee-Replacement Patients and Complications” first appeared as a post on the Regenexx blog.