An $87,500 bill for a 20-minute knee procedure is just an extreme example of high amounts that insurers are billed by out-of-network surgery centers, experts say. Insurers are starting to fight back.

A Southern California surgery center charged a Long Beach Unified School District teacher $87,500 for a routine, 20-minute knee operation that normally costs about $3,000. According to the report in the Los Angeles Times, despite the huge markup, the Long Beach Unified School District and its insurer, Blue Shield of California, paid virtually all of the bill from Advanced Surgical Partners in Costa Mesa. Blue Shield mailed the $84,800 check to the high school Spanish teacher last month and told her to sign it over to the surgery center.

This case points to a growing battle nationwide over billing by outpatient surgery centers. Industry experts say some of these surgery centers seek out well-insured patients, sometimes by waiving their copays and deductibles, and then bill their insurers exorbitant amounts for out-of-network care. All too often, critics say, insurers pay these large sums and then cite high medical bills for why insurance premiums keep rising for businesses and consumers.

In response to questions from The Times, Blue Shield defended its $84,800 payment as proper. Advanced Surgical Partners, through its lawyer, said the bill was excessive. Amid the scrutiny, the two sides agreed to a lower amount this week. Henry Fenton, an attorney for the surgery center, said this bill “was excessive and not correct. I’m sure they will be more careful in the future.” Blue Shield said its typical rate for this arthroscopic knee procedure in Southern California is about $3,000 among in-network providers.

“This surgery center is charging 30 times the average by remaining out of network to advance this outrageous and anti-consumer practice,” said Blue Shield spokesman Steve Shivinsky. “This is a national problem.” Yet the company said it was obligated to pay nearly all of Advanced Surgical’s bill because it is bound by the health plan rules set by the teacher’s employer, the Long Beach school district. The school system is self-insured, meaning it pays its own medical bills and uses Blue Shield to administer its benefits and process claims.

In other situations involving out-of-network care, it’s common for insurers to pay only about 60% of what’s deemed to be “usual and customary” charges or some percentage of Medicare rates. Insurers and out-of-network medical providers routinely spar over what constitutes a reasonable amount. Kominski, a UCLA professor, said he faulted both Blue Shield and the school district for “dropping the ball on this. There were lots of opportunities for red flags to go off on such an outlandish bill.”

Nationwide, some insurers have begun to challenge these bills from outpatient centers. Last year, a unit of insurance giant Aetna Inc. sued several surgery centers in Northern California and accused them of overbilling the insurer more than $20 million. It has pursued similar actions against providers in New Jersey and Texas. Other insurers such as UnitedHealth Group Inc. have filed similar suits in California.

In one instance, Aetna said, a California surgery center charged $73,536 for a kidney stone procedure when the average in-network charge was $7,612. Aetna said it paid some of these bills before disputing them in court.

Doctors and surgery centers say the criticism is unjustified. Surgery centers say they have helped reduce healthcare costs by offering convenient care at a fraction of what hospitals charge for colonoscopies, cataract surgeries and other outpatient procedures. These facilities now handle up to 40% of all outpatient surgeries, according to the Ambulatory Surgery Center Assn.