They came with the promise of a firm tush and taut thighs, but what toning shoes have delivered are claims of injuries from consumers, headaches for their makers and a bounty of legal work for plaintiffs firms.

At least 90 personal injury lawsuits are pending in federal and state court against Skechers USA Inc., maker of Shape Ups, the shoe with a thick, curved sole touted as helping people who wear them during everyday activities lose weight and get fit. The plaintiffs claim that, rather than providing an easy way to slim down, the round-bottomed shoes are dangerously unstable, resulting in broken ankles, busted knees, even head injuries. Skechers has the biggest share of the toning-shoe market, which dropped from $1.1 billion in 2010 to about $550 million in sales last year, according to SportsOneSource, a research firm in Charlotte, N.C. Skechers has about 49 percent of the market while Reebok International Ltd. and a handful of other manufacturers control the rest, said Matt Powell, a SportsOneSource analyst.

Skechers paid about $50 million on May 16 to settle a class action brought by the Federal Trade Commission and attorneys general in 44 states, alleging that the company falsely promised users that they’d get in shape by wearing the shoes. Reebok, which made Easy Tone shoes, paid $25 million last year to resolve similar FTC claims. Neither company admitted any wrongdoing. The settlement proceeds went primarily to reimbursing consumers who had bought the shoes, which cost between $60 and $100 per pair.

CLAIMS OF INJURY

The false-advertising claims were just the beginning. What remains is the potential for hundreds of millions of dollars in actual and punitive damages from personal injury claims — and plenty of fees for lawyers representing consumers swayed by the promise of easy fitness.

The design of the shoes, according to their makers, enables users to engage their gluteal muscles, hamstrings and calf muscles while performing everyday activities — more so than with regular shoes. But consumers and their attorneys argue that toning shoes create an unstable walking surface and interfere with the user’s normal gait, causing repetitive stress injuries and, in some cases, fractured bones and head injuries from falls.

About 30 cases against Skechers were consolidated in December in the U.S. District Court for the Western District of Kentucky. Senior Judge Thomas Russell is presiding over the multidistrict litigation, with Janet, Jenner & Suggs in Baltimore as co-lead counsel along with Schachter, Hendy & Johnson in Fort Wright, Ky. At the same time, about 60 plaintiffs have brought cases in California state court, represented by San Diego-based Estey Bomberger. About 50 additional plaintiffs have retained the law firm but have not yet filed, said attorney Michael Bomberger. Skechers is the defendant in the vast majority of toning-shoe cases, mainly because of its dominance in the market, Bomberger said.

Representing Skechers in the personal injury cases are O’Melveny & Myers and Dinsmore & Shohl. Daniel Petrocelli, a partner at O’Melveny who is working for Skechers on the matters, did not respond to repeated requests for comment about the personal injury litigation. A Skechers spokesman referred to a press release the company issued following the May 16 settlement. In it, the company said it continues to stand behind its toning shoes and that it paid the FTC settlement “in order to avoid protracted legal proceedings.”

Meanwhile, dozens of personal injury firms across the country are ginning up ads for broadcast on television and the Internet, asking consumers who were hurt while wearing toning shoes to contact them.

Edgar Snyder & Associates, with five offices in Pennsylvania, offers “live chat” sessions with attorneys over the Internet to help potential plaintiffs. Schachter, Hendy & Johnson, handling some of the federal claims, has acquired the Internet domain name “toningshoesinjurylawyer” and operates a Web site providing information for consumers who bought toning shoes made by Skechers, FitFlops, New Balance Athletic Shoe Inc., Dr. Scholl’s and Easy Spirit. Galligan & Reid, in Des Moines, Iowa, offers free consultations for buyers who have suffered bone, joint and tendon problems from the shoes.

Davis & Crump in Gulfport, Miss., and many other law firms have posted on their Web sites a photo of a woman wearing pink medical scrubs and round-bottomed shoes slumped in pain as she clutches her lower back. On television, the late-night airwaves are replete with ads for law firms in search of clients who might have claims.

It’s likely that Skechers and other defendants will settle these claims instead of defending them at trial, a process that still could take years, said Mary Davis, a law professor at the University of Kentucky College of Law whose scholarship focuses on products liability law. If the cases do go to trial, the federal actions probably will proceed in multidistrict litigation through the discovery process and then will go back to their original jurisdictions for trial, Davis said.

For plaintiffs, the easiest approach could be to pursue claims of failure to warn, instead of arguing that the shoes’ design was flawed, she said. “With failure to warn, you don’t have to challenge the features of the product. You’re challenging the communication of the risk,” Davis said.

Challenges to the design, she said, generally would require the plaintiffs to demonstrate that an alterative design was better, which can be tricky and expensive.

In her case, Lisa Fuller, a 45-year-old from Mountain View, Ark., claimed strict liability, negligence, breach of warranty and fraud in addition to a failure to warn. Her lawsuit against Skechers was originally filed in Arkansas federal court in September and is now part of the multidistrict litigation in Kentucky.

Two years ago, Fuller saw a Skechers ad on TV. She wanted to shed a few pounds and liked the idea of getting in shape with little effort. “They were showing a lady shopping and going about her everyday business,” Fuller said. “I thought, ‘That’s a lifestyle change that I can do.’ ”

Fuller bought a pair at a mall in West Monroe, La. The thick soles made her feel tall, she said. In December 2010, as she and her husband were walking in downtown Mountain View, a “cute little tourist town with eateries and fancy shops,” said Fuller, she toppled from her toning shoes, breaking both her ankles, she said.

“I screamed so loud I was embarrassed,” she said. Fuller, who said she had never broken a bone before, noted that her left ankle required eight pins. “I now warn people not to buy those shoes,” she said.

In its answers to the personal injury complaints, Skechers largely has claimed a lack of information to form an opinion about the truth of the claims and denied the allegations outright — standard responses in the early stages of litigation. The company also has asserted affirmative defenses including statute of limitations, assumption of risk, misuse by the consumer and unforeseeable injuries.

The toning-shoe litigation, Davis said, is unlikely to prompt widespread claims against the makers of other arguably unstable shoes such as platforms or stilettos, popular choices for women today. Because manufacturers generally do not have a duty to warn of “obvious dangers,” it would be difficult to make such a claim involving those types of footwear, she said.

“You don’t have to tell people that you might fall if you’re wearing a high-heeled shoe,” she said.

Leigh Jones can be contacted at ljones@alm.com.