Ads featuring TV personality Kim Kardashian claim Skechers Shape-Up shoes promote weight loss, reduce joint stress and improve coordination — all without going to the gym.

But a suit in federal court in Trenton alleges the rocker-soled shoes not only fall short of those claims but also alter gait mechanics and create instability, putting wearers at risk of injury.

In Valdez v. Skechers, 13-cv-01799, plaintiff Donna Valdez of Freehold says she was wearing the Shape-Ups last April 29 while sitting on a porch railing. When she stepped to the ground, her left shoe turned outward and rolled sideways, causing an ankle fracture, she claims.

Valdez alleges the claims of health improvement were false and she would not have bought the shoes if she knew that in advance.

One of Valdez’s lawyers, Freehold solo Steven Gabor, says an expert witness will explain how the shoes’ unusual design contributed to the accident.

He says Valdez has returned to her job as an administrative assistant but walks with some difficulty.

She claims she suffered physical pain and mental anguish and is at increased risk for future health problems and disability.

Her suit includes counts for strict liability, negligence, breach of express warranty and of implied warranty of merchantability, and for New Jersey Consumer Fraud Act violations.

Valdez sued in Monmouth County Superior Court on Feb. 6, and Skechers USA, of Manhattan Beach, Calif., removed the suit to federal court on March 22.

The removal petition was filed by Steven Wiederhorn of Faust, Goetz, Schenker & Blee in Livingston, who did not return a call.

A Skechers USA spokeswoman, Jenn Clay, says the company will not comment on the suit, but she points to information posted on a company website, shapeupsmediainfo.com.

It says Shape-Ups users should "first get accustomed to the shoes before walking significant distances or wearing them for significant periods of time."

It also says, "The low rate of injuries reported compared to millions of pairs of Shape-Ups sold, combined with the thousands of unsolicited testimonials we have received from satisfied customers who reported no safety or physical concerns, reaffirms our believe that Shape-Ups are safe."

In addition, the site says that while "a number of personal injury suits" have been filed over the Shape-Ups, "none of these cases has resulted in any findings or judgments against the company, and such actions and complaints are not unusual for athletic exercise equipment."

In May 2012, Skechers USA agreed to pay $40 million to settle charges by the Federal Trade Commission that it made unfounded claims that Shape-Ups would help people lose weight and strengthen and tone their buttocks, legs and abdominal muscles.

"Skechers’ unfounded claims went beyond stronger and more toned muscles. The company even made claims about weight loss and cardiovascular health," said David Vladeck, director of the FTC’s Bureau of Consumer Protection.

"The FTC’s message, for Skechers and other national advertisers, is to shape up your substantiation or tone down your claims," he added.

Valdez is also represented by Freehold solo B. David Jarashow.