Latest research shows that cigarette smoking could impair the healing of injuries to the ligament - a short, strong band of tissue that connects bones to other bones to form a joint.
Studying mice with knee ligament injuries, the researchers at the Washington University School of Medicine discovered that smoking impairs the recruitment of cells to the injury site and delays healing following ligament-repair surgery.
The soft tissue healing that occurs following ligament injuries occurs in stages. There is an immediate pooling of blood near the injury that causes swelling right away.
This initial response is followed by several days of inflammation in which cells called macrophages flock to the injury site and secrete substances called cytokines and chemokines. Those, in turn, recruit more cells to assist in healing.
This process lasts for several days. The final stage of healing involves remodelling of the tissue and can continue for months and even years.
To look at the effects of smoking the researchers used a system in which mice are placed inside smoking chambers six days per week, reported online edition of the Newswise .
The mice didn't actually have cigarettes in their mouths, but they got enough passive fumes to "smoke" two cigarettes daily, the equivalent of a person smoking about four packs per day.
Mice were placed in the smoking chambers for two months prior to ligament surgery and then again after surgery to mimic the behaviour of humans who continue to smoke following an injury.
The researchers said their findings point to yet another reason smokers would do well to quit.