GRAND RAPIDS, MI -- A lawsuit filed by 18 alleged victims of Dr. Larry Nassar claims a series of institutional failures perpetuated his access to the young females he is accused of abusing.

"For over 20 years, Defendant Nassar had unfettered access to young female athletes through the Sports Medicine Clinic at MSU, and through his involvement with USAG and Twistars, who referred athletes to his care," reads the lawsuit, which names, as defendants, Michigan State University, USA Gymnastics, Nassar and Twistars, a Lansing-area gymnastics training facility.

The lawsuit was filed in U.S. District Court on Tuesday by attorneys Stephen Drew, Adam Sturdivant, John Manly, Vince Finaldi and Alex Cunny. They represent 18 plaintiffs who allege they were sexually abused by Nassar, including some who are still minors.

This action joins another civil lawsuit pending in Ingham County Circuit Court.

Nassar, who worked in MSU's sports medicine clinic, is the subject of separate criminal charges at both the state and federal levels. Attorney General Bill Schuette is moving forward with a criminal sexual asasult case, but police say they have received more than 50 other complaints against Nassar. He's also facing federal child pornography charges.

Plaintiffs in the civil suit hope their suit against the institutions Nassar worked for brings about institutional change, attorneys said.

"If you have the right systems in place and you vigorously enforce them and you send a message that 'we are going to vigorously enforce them,' that's how you stop these type of things from happening. You don't discourage people from making complaints," said Drew, an attorney for the plaintiffs.

He said his clients, most of whom remain anonymous in the lawsuit, had in some cases alerted the university to Nassar's methods, which allegedly involved things like digital penetration of the vagina or anus and non-consensual touching of breasts.

One plaintiff who has come forward publicly is Rachael Denhollander, who spoke Tuesday at a press conference announcing the suit's filing.

She said she visited Nassar five times for hip and back pain, and he digitally penetrated her under the guise of medical treatment. She said the institutional prominence that MSU and USA Gymnastics had afforded Nassar made her believe he used legitimate medical procedures.

Now, she's part of the suit because she hopes it brings about institutional change and protects girls and young women in the future.

"The reality of sexual abuse is this: A pedophile is only as prominent as the people around him allow him to be," Denhollander said.

There are 17 other women identified in the suit. According to the complaint, all plaintiffs are or were young athletes participating in swimming, figure skating, track and field, field hockey, basketball, gymnastics or soccer. They are seeking compensatory damages, punitive damages and attorney fees in addition to institutional change.

USA Gymnastics and MSU have severed ties with Nassar.

Asked for comment on the lawsuit, MSU issued a statement:

"While we cannot comment specifically on pending or ongoing litigation, we are deeply disturbed by the state and federal criminal charges against Larry Nassar, and our hearts go out to those directly affected."

USA Gymnastics issued a statement as well.

"USA Gymnastics finds the allegations against Dr. Nassar very disturbing. When we first learned of athlete concerns regarding Dr. Nassar in the summer of 2015, we immediately notified the FBI and relieved him of any further assignments. USA Gymnastics has fully cooperated with the FBI in its investigation," the organization said.

"We find it appalling that anyone would exploit a young athlete or child in this manner, and we are grateful to the athletes who have come forward."