Differences in Resident Knee Stem Cells Explain why ACL’s heal more slowly than MCL’s
The main ligaments of the knee heal at different rates, with the MCL healing better than the ACL. The MCL is the ligament on the inside of the knee that helps keep the side of the knee together, while the ACL is in the center of the knee and helps keep the tibia bone from sliding forward on the femur. It’s been assumed that the reason one healed more slowly than the other was because the MCL had a better blood supply, but now a new study suggests that it may be a stem cell effect. We now know that just about every part of our body has resident adult stem cells responsible for local maintenance and repair of the tissue, so the fact that these important knee ligaments have stem cells inside them isn’t at all surprising. However, researchers recently asked the obvious question, do stem cells in these ligaments grow at different rates and is that why one heals better than the other? The answer is that the stem cells inside the ACL ligament do in fact grow more slowly than the MCL knee stem cells that live in that ligament and this may explain the differences seen in healing rates. This big difference in stem cells from two ligaments in the same joint also points to just how different stem cells are from site to site. As I’ve said before, where you get your stem cells seems to be very important. For example, bone marrow stem cells are better than fat stem cells for producing cartilage. In addition, the fact that both of these structures have stem cells means that using stem cells to augment their healing is a natural phenomenon. The upshot? Stem cells are everywhere in our bodies. As a result, in our view they’re important body parts that can be used to help orthopedic tissues help repair themselves.