Anterior cruciate ligament (ACL) tears are among the most frequent traumatic knee injuries in both professional and recreational athletes.
But despite the fact that surgical procedures to repair the injuries have good outcomes, many patients face lengthy periods of muscle atrophy.
“Even with our best efforts in terms of rehabilitation, when we send patients back out to play sports, they still have muscle weakness at the site of the tear, particularly at the quadriceps, the main thigh muscle extending from the knee,” says Christopher Mendias, Ph.D., associate professor of orthopaedic surgery, and molecular and integrative physiology. “Short term, patients are weaker on that knee and could get reinjured. Long term, what we see is a very good chance of developing osteoarthritis and eventually needing a knee replacement.”
Mendias explains that normally during exercises, such as jogging, forces are transmitted through the muscles. If the muscles are weak, those forces will instead travel through the bones, hitting the cartilage that connects the bone to the joints.
“You’re looking at decades of having a painful knee,” Mendias says. “It’s a slow process in which the cartilage erodes. Average weekend warriors may need to wait six months after ACL surgery to return to normal activity. For professional athletes, that time is likely to be up to 11 months.”
With $800,000 in funding from the Mark Cuban Foundation, Mendias and his colleague, Asheesh Bedi, MD, service chief for sports medicine and associate professor of orthopaedic surgery, are now studying human growth hormone (HGH) as a potential means to preserve the strength of the thigh musculature that would otherwise be lost through an ACL tear and resulting treatment.
The clinical trial will compare HGH with a placebo in 50 men, ages 18 to 35, who have had a recent ACL tear, but no previous major knee injuries.
Participants will inject themselves with HGH or a placebo twice daily, starting a week before surgery and continuing until five weeks after surgery. The investigators will use magnetic resonance imaging and muscle strength tests to compare both knees during the course of therapy and up to six months after surgery, and will collect patients’ experiences with the supplement. Women are excluded from the study because of concerns about HGH’s effect on a developing fetus.
“Once muscle is lost, it’s really hard to get that strength all the way back,” Mendias says. “The idea is that by administering growth hormone in that early stage after the ACL tear, we can prevent some of the loss in muscle mass. Then, patients will have a stronger base to work on during rehabilitation following surgery.”
HGH, which stimulates cell growth and cell regeneration, is available only by prescription for a small list of approved uses, such as childhood growth disorders and wasting disease. But, it has been shown to protect against muscle weakness in some basic science studies.
HGH has been banned by some professional sports organizations, but Mendias says that while the hormone does shrink fat and cause muscle tissue to absorb water and improve definition, it does not enhance athletic performance, so there are no doping effects on otherwise healthy muscle.
Mendias and Bedi received approval from the U.S. Food and Drug Administration to conduct the two-year study. If the study is successful by its completion in late 2017, Mendias will approach the FDA about expanding the study to more patients in additional locations.