Niners wide receiver Ricky Pearsall tests his injured right knee on May 28 duringoffseason team activities at the Levi's Stadium practice field. (Santiago Mejia/S.F. Chronicle) Wide receiver Ricky Pearsall sprained the posterior cruciate ligament in his right knee Sept. 28. More than 10 months later, after he'd returned to play in six-late season games, suffered multiple aggravations and had an offseason of rehabilitation- the injury still hadn't healed.On Saturday,San Francisco 49ers general manager John Lynch announced the 2024 first-round pick would undergo PCL reconstruction surgery that will end his 2026 season.Why did it take so long to reach that decision? Lynch said Pearsall's case was unusual. Most isolated PCL injuries heal without surgery. Pearsall's did not.That explanation makes sense to Dr. Prem Ramkumar, an orthopedic knee and hip surgeon who consults for the X Games and Long Beach State athletics. In fact, Ramkumar said surgery for an isolated PCL injury is so rare among professional athletes that there isn't enough data to confidently predict whether Pearsall will return to his pre-injury form in 2027.Ramkumar mentioned only one prominent professional athlete whose situation closely resembled Pearsall's: NBA center Steven Adams underwent surgery for an isolated PCL injury in November 2023, about 10 months after he was hurt."Isolated PCL injuries do not typically require surgery," said Ramkumar, who works at MemorialCare Long Beach Medical Center. "We usually operate when a patient has failed nonsurgical treatment for several months, if not years."Like the anterior cruciate ligament, the PCL helps stabilize the knee. Unlike with an ACL injury, however, reconstructing a damaged PCL often does not provide substantially more stability than allowing the ligament to scar and heal without surgery, Ramkumar said.Pearsall was sidelined for six games- or 47 days- after he was initially hurt last season in a Week 4 loss to the Jaguars. Pearsall was medically cleared by team doctors. He also received a second opinion before he returned to play."At some point, you have to test the knee," Ramkumar said. "You are bringing what you believe is a healed PCL back into competition to see whether it can do the job. He may have felt fine while running certain routes in a controlled environment. Then he encountered the unpredictability of a game, and the knee did not hold up."Backup quarterback Mac Jones' recovery was more typical. Jones suffered a similar PCL injury on Aug. 16, but he was able to make his first fill-in start on Sept. 14. He aggravated the injury on Sept. 21, but he still made eight consecutive starts, ranking second in the NFL in completion percentage, before returning to his No. 2 role when Brock Purdy recovered from a toe injury.Pearsall's return was far less successful. He never finished more than three consecutive games. He aggravated the injury in Week 15 and missed the following game. He aggravated it again in Week 17 and sat out the next two.His production also suffered. Pearsall had fewer than 15 receiving yards in four of the six games he played after returning. As an outside observer, Ramkumar said he didn't know whether the six late-season games in whichPearsall played could have complicated his recovery."I cannot definitively say whether his attempts to play made his injury worse," Ramkumar said.Pearsall then had several months of rest and rehabilitation during the offseason. So why did the injury still fail to heal?Ramkumar said doctors do not fully understand why isolated PCL injuries occasionally require surgery. One possibility, he said, involves "individual biology"- something about the structure of Pearsall's knee that made nonsurgical treatment less likely to succeed.Pearsall experienced swelling in the knee last month after participating in the first two training-camp practices. That setback prompted the decision, made in consultation with team doctors and independent surgeons, to operate.The lengthy rehabilitation also explains why Pearsall and the 49ers decided against surgery after the 2025 season. Had Pearsall undergone the procedure in January, he still might have missed most or all of the 2026 season. Lynch said Pearsall's recovery is expected to take six to 12 months. Ramkumar said he would not clear an athlete to return from PCL reconstruction for at least nine months, allowing the graft sufficient time to mature.Lynch said Saturday that Pearsall would have surgery in the next few weeks. The complexity of the procedure is another reason doctors exhaust nonsurgical options before operating. Ramkumar explained that the surgeon must drill near the back of the knee, close to the popliteal artery, a major blood vessel. Damage to the artery could put the patient's leg at risk."It is a very technically challenging operation with significant risks," Ramkumar said. "You need an excellent surgeon to perform it."SubscribeTheres more to San Francisco with the Chronicle. Subscribe today for just 25.This article originally published at Why Ricky Pearsall's rare PCL surgery was the 49ers' last resort: Significant risks'.