Former Clemson quarterback Deshaun Watson runs for a touchdown.

Deshaun Watson famously played in a game with a torn ACL. New research will help fine-tune ACL rehab to get people back in action quickly.
Image Credit: David Platt

CLEMSON, South Carolina — Former Clemson quarterback Deshaun Watson famously played in a 2014 game with a torn ACL. This season, he was burning up the NFL record book when the ACL in his other knee snapped, ending his season and breaking the hearts of tens of thousands of fans.

The former Clemson University star has a lot of company on the sideline. As many as 250,000 people each year in the United States get benched by an injury to the anterior cruciate ligament, or ACL.

Despite the prevalence of the injury, there continues to be scientific debate about how to more effectively rehabilitate the knee after reconstructive surgery. As a result, methods and outcomes vary; one-third of people recovering from an ACL tear don’t return to sports within a year, and 25 percent who do return will injure their knee a second time.

“Over the course of a year, you may begin to do more activity on your injured leg, but the question is whether the muscles regain full strength,” says John DesJardins, an associate professor of bioengineering at Clemson.

Researchers at Clemson University, where Watson led the Tigers to the 2016 National Football Championship, and nearby Furman University, have taken a step toward understanding the vulnerable ligament, which acts like a seatbelt for the knee, keeping the lower leg bone from flying through the joint during sudden stops.

Previous research showed that people going through rehabilitation after ACL reconstruction avoid using their quadriceps – the group of muscles in the front of the upper leg that allows the leg to extend. They rely on their hamstrings – the muscles on the back of the upper leg that allow the leg to flex. As a result, the quads lose strength and the knee takes longer to fully recover.

Therapists often use a stationary bike in ACL rehab programs, but there are different methods. Sometimes the patient pedals with both legs, sometimes they pedal with only the injured leg.

At Furman’s Molnar Human Performance Lab, Randy Hutchison, associate professor of health science, and Clemson’s John DesJardins, associate professor of bioengineering, put 17 people through a stationary cycling trial; seven were within a year of ACL reconstruction surgery and 10 had no history of an ACL injury. Their work was published in the Journal of Functional Morphology and Kinesiology.

Man on a stationary bike with sensors on his leg peddles in an ACL study.

New research shows that peddling with one leg can be important to fine-tune ACL rehab.

According to the Clemson-Furman research, people without an ACL injury who pedaled a stationary bike with both legs used their quadriceps muscles much more than their hamstrings. But when they pedaled with only one leg, the reverse was true – hamstrings took over for the quads.

However, people recovering from ACL repair used both quads and hamstrings almost equally, whether they pedaled with one leg at a time or with both.

“This work helped show that therapists could ‘tune’ the treatment options for individual patients, and use both double- and single-legged pedaling to activate the appropriate muscle groups for a more individualized treatment,” Hutchinson says.

The goal is to help someone recover fully, and return to activities as soon as possible,” DesJardins says. “The idea that we can work with recovering athletes and physical therapists to make rehabilitation treatments more effective is great.”