Starting in the first trimester, the woman's body begins to produce a hormone called relaxin. The hormone helps the expectant mother to loosen muscles, joints and ligaments. In this way the body makes less effort to adapt to the growing child. A multidisciplinary team from the BIMDC (Department of Orthopedic Surgery at Beth Israel Deaconess Medical Center) studied the effects of relaxin on patients with arthrofibrosis.
The study starts from the observation of some pregnant patients. Some women suffering from the disease reported a reduction in pain both during gestation and immediately afterwards. The doctors looked for a possible cause of the phenomenon, focusing on the production of relaxin. At this point, they decided to check whether their suspicions were founded or not.
The doctors injected human relaxin into the joints of some guinea pigs. The animals suffered from a painful form of arthrofibrosis, which prevented them from using their shoulders. This is a particularly debilitating variant, common especially among middle-aged and diabetic women. The guinea pigs treated in this way have recovered much of their mobility; tissue samples showed improvement even at the cellular level. In a second study, the team analyzed relaxin-2. This version of the hormone inhibits the production of scar tissue by lowering the levels of collagen which, in excessive quantities, accelerates the phenomenon.
Injections made with relaxin-2 brought more significant and even more lasting improvements. One of the next steps will be to test the effects of the hormone on humans, but further tests will be needed first.