Two decades ago, a patient having a hip or knee replacement could expect to spend three to five days in the hospital. Today, some go home within hours of surgery, a shift driven by a series of clinical and technical advances that have made the procedure faster and more durable than ever.
Daniel Sun, MD, an orthopedic surgeon at Boston-based Tufts Medical Center and an assistant professor at Tufts University School of Medicine in Boston, credits those advances. But he sees a gap opening between how fast the field can safely move and how fast CMS wants it to — and argues that under bundled payment, slowing down for safety is also the financially sound choice.
Dr. Sun points first not to the operation itself, but to how patients are managed around it.
“I think that our modern protocols for getting patients up and moving have really been the biggest difference maker,” Dr. Sun said during an interview with Becker’s.
Much of that comes down to coordination across the perioperative team, including anesthesia, physical therapy and nursing.
“The biggest thing has been that we collaborate a lot with the anesthesiologists at our hospital,” he said. “We have a meeting every month just to make sure we’re all remaining on the same page.”
Agreement on shorter-acting spinal anesthetics, nerve blocks and standardized pain medication protocols before and after surgery has sped recovery for patients, he said.
The implants have improved, too. Dr. Sun said the advance that has made the biggest measurable difference for patients isn’t one of the field’s more heavily marketed technologies, but highly cross-linked polyethylene, the plastic bearing surface. Wear in older plastics caused bone resorption and related complications. The newer material has helped address that problem, and hip replacements are lasting longer as a result.
Those gains have made same-day surgery possible for many patients. For patients who qualify, outpatient surgery has worked well, he said, and most recover better at home than in a hospital room where they are woken every few hours. But Dr. Sun draws a distinction he believes can get lost in the push toward outpatient care.
“It’s important to distinguish between faster discharge and faster recovery,” he said. “CMS is definitely pushing for faster discharges. Whether that’s necessarily associated with faster recovery or not, I think it’s a little bit patient-dependent.”
Dr. Sun said he is especially hesitant as CMS pushes increasingly complex cases to the outpatient model. CMS’ 2026 outpatient payment rule added revision total hip and knee arthroplasty to the ambulatory surgery center covered procedures list and began a three-year phaseout of the inpatient-only list, starting with 285 musculoskeletal procedures.
“Obviously CMS is really pushing things forward and I think they’re pushing the pace at this point faster than the surgeons are,” Dr. Sun said. “For example, this year CMS decided that revision hip and revision knee could be outpatient procedures, which in my opinion is a little fast.”
Revision cases vary widely and carry considerable complexity, he said. He understands CMS’ interest in lowering costs, but he worries the policy changes the calculus for surgeons.
“I think pushing it towards the outpatient coding system is almost encouraging surgeons to kind of take on a little bit more risk,” he said.
That risk also carries a cost. Under CMS’ Transforming Episode Accountability Model, which took effect Jan. 1, participating hospitals are paid based on the total cost and quality of a joint replacement, from surgery through recovery. Dr. Sun argues the incentives in that model point in the same direction as good clinical care.
“It’s important to recognize that patient safety and financial loss go hand in hand,” he said. “If a patient is not safely taken care of and they come back to the hospital, that’s a huge financial hit for you in a bundled payment system. Whereas, you just maybe spent a little bit more on patient safety. Sure, your margin might be a little bit thinner. But in the end, everybody kind of wins.”
The case for caution is rooted in the complication the field has not been able to engineer away. Despite years of effort, Dr. Sun said, the rate of infection after joint replacement has barely moved, and infection remains a leading reason patients need revision surgery, along with mechanical instability and fractures.
“We’ve tried a lot of different things,” he said. “The rate of people who get that complication has stayed relatively the same despite a lot of the different things that we’ve tried.”
That is part of why surgeons have moved toward optimizing patients before surgery rather than scheduling it as soon as arthritis is diagnosed.
“Most hip and knee surgeons out there are making sure that everything that can be optimized is optimized so that we can decrease the risk of all these complications and give the patients the best experience possible,” he said.
It is also why Dr. Sun wants patients and referring physicians to recalibrate their expectations, even as same-day discharge becomes routine.
“Although hip replacement is one of the most common procedures we do and the vast majority of patients love their hip replacement and get through the surgical episodes without a hitch, it is not a minor procedure,” he said. “I think sometimes patients come in asking for a hip replacement or other referring physicians tell patients to get a hip replacement, almost treating it like a teeth cleaning when it’s actually a pretty major procedure with some real complications.”
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