The knee replacement market has reached stratospheric levels in the U.S., with competitors ranging from Zimmer Biomet (NYSE:ZBH) to Smith & Nephew (NYSE:SNN) and Johnson & Johnson (NYSE:JNJ). California device developer Moximed is betting its future, however, on patients not quite ready for the drastic surgery.

The knee replacement market is worth an estimated $4 billion in the U.S., and knee replacements have been the most common inpatient hospital procedure for folks over age 45 since 2008. Moximed, based in Hayward, Calif., believes it can grab a big part of that market with its Atlas device, a reversible implant designed to buy more time for patients who have moderate knee trouble and might need an implant in the future.

Atlas is designed to treat osteoarthritis knee joint pain in patients ages 35 to 65 whose condition has not degenerated enough to require arthroplasty. The device is a joint unloader placed along the knee to absorb excess load and buy time. The cylindrical shock absorber component is about as long as a standard house key and has the diameter of a pencil, and the bases that attach to the bone have a footprint a bit larger than a quarter. Once the osteoarthritis becomes too severe, Atlas can be taken out to make room for a full knee replacement as needed.

CEO Kevin Sidow told MassDevice.com that he sees Atlas standing out for those reasons, the idea that it can potentially “allow patients to live the fully active lifestyle they deserve, while at the same time preserving all of their downstream therapeutic options.”

“Joint unloading is a clinically proven and established concept among orthopedic surgeons, but none of the current forms of joint unloading are well accepted because they negatively impact patient lifestyles,” Sidow told us.

What alternative treatment options are there? Not many. Sidow noted treatments such as Advil and hyaluronic acid injections (which can work for a time and then be less effective with future injections).

With that in mind, the premise behind Atlas has been enough for Moximed to raise approximately $100 million since its 2007 launch, including a $33 million Series B round in May. Investors including New Enterprise Associates, Gilde Healthcare Associates, Morgenthaler Ventures, GBS Venture Partners and Vertex Venture Holdings have all taken a stake in the idea.

Sidow, in charge since 2008, can point to results. In late November, Moximed, which also has offices in Zurich, gained a CE Mark approval in the European Union for Atlas. But all attention now is focused on a U.S. approval strategy, for which Sidow is thinking outside of the box.

Atlas is essentially the next-generation version of KineSpring, an earlier product that has limited approval. KineSpring is at the center of a 310-patient study that will be submitted to the FDA, for a PMA or possible de novo approval.

At the same time, however, Moximed is accumulating European data for Atlas under the CE Mark. Sidow said that this data, plus data collected under a U.S. investigational device exemption trial once approved, could be used in tandem with the KineSpring data for a U.S. marketing submission.

“What we hope to show with data for Atlas is that it has the same effectiveness as KineSpring in alleviating patients'” knee pain, Sidow said. “It has some advantages; it is smaller [than KineSpring], the surgical technique is more straightforward and there is a shorter operating time.”

Sidow said Maximed hopes to be able to show the FDA comparable or slightly better data from the Atlas device (newer and potentially better), at the same time it’s reviewing the KineSpring product. If this can happen, Sidow said he wants to work with regulators to find a way that allows for clearance or approval for Atlas in the U.S. market. Looking ahead, Sidow said that Moximed hopes to raise another round in late 2016 and pursue more Atlas data to help with its U.S. approval and an eventual reimbursement strategy.

The plan is also to build a strong, independent company, though being acquired is at least an indirect option.

“My philosophy on this is to build a company that can stand on its own,” Sidow said. “If somebody taps you on the shoulder and makes an offer you can’t refuse, then that is a situation of shareholders and the board making a strategic decision.”

Sidow added, however, that Atlas is being readied for a “massive market opportunity” with a “tremendous unmet need for patients.” With that under consideration, Sidow said it is “why we don’t want to be in a hurry to sell the company.”

“It is why we want to build something free standing,” Sidow said.