The play called for a reverse punt return, an odd decision since the Chicago Bears already held a comfortable lead on the New England Patriots in the 1985 Super Bowl. Bears returner Keith Ortego signaled a fair catch before deciding to hand the ball to Leslie Frazier, whose left foot got stuck in the Louisiana Superdome's turf.

Frazier's career was over.

He suffered extensive damage in his knee, the most severe being a torn anterior cruciate ligament, which required reconstructive surgery. He spent the following season on injured reserve for the Bears and then failed a physical in training camp in 1987. He accepted a tryout with the Philadelphia Eagles, but he wasn't the same player and retired.

"I just couldn't get my range of motion," Frazier said. "I couldn't sprint."

The Vikings coach reflected on his experience with ACL surgery an hour after witnessing All-Pro running back Adrian Peterson sprint up a steep hill abutting the team's practice field at the five-month mark of his ACL rehabilitation.

Frazier smiled and shook his head.

"It's a totally different procedure than when I had mine," he said. "It's no comparison. The cut on my knee looks a lot different than the cut on Adrian's knee."

Advances in technology and rehab protocol in ACL reconstruction the past two decades have improved the long-term prognosis for athletes and enabled them to return to competition significantly faster. A normal timeline for return from ACL surgery now is six to nine months, which is encouraging news for Twin Cities sports fans tracking the progress of three high-profile athletes in the midst of ACL rehab -- Peterson, Timberwolves point guard Ricky Rubio and Gophers forward Trevor Mbakwe.

Doctors note that ACL surgery and rehab vary by patient, but the injury has become so common that nearly 100,000 reconstructions are performed in the United States each year, according to medical literature. Athletes still view ACL surgery as a significant career setback that promises a long, arduous recovery process. Many also acknowledge that they didn't feel completely normal until their second full season after surgery. But medical improvements and overall awareness of the injury provide a much brighter outlook nowadays.

"You put the best technology with the most motivated person, you get some spectacular results," said Randy Twito, a HealthPartners Medical Group physician who practices at Regions Hospital.

Twito, a veteran surgeon, has witnessed the procedure's transformation over the years. One example: Previously, patients had their knee immobilized in a cast after surgery so that it would stiffen. Now, many patients awake from surgery with their knee in a machine that stimulates range of motion in order to avoid stiffness.

"It's such a perfect science now so they're efficient," Vikings head athletic trainer Eric Sugarman said.

Surgery advances

Dr. David Fischer, the Timberwolves' orthopedic surgeon since their inception, began performing ACL surgery in his practice in the late 1970s when, he notes, "we really didn't know much about this injury at all."

Surgery was performed on an open knee because arthroscopic technology was still developing. Surgeons experimented with different tissue grafts to replace the torn ligament, including synthetic material, allografts (donor tissue from a cadaver) and xenografts (animal tissue). Eventually, doctors found the most successful grafts come from the patient's own patellar tendon or hamstring tendon.

Advancements in science, technology and surgical techniques over the years made surgery less invasive. Doctors also gained a better understanding of the ideal placement of the graft inside the knee. Those improvements led to better results and more confidence that the knee could withstand physical punishment at the same force as preinjury.

Early postoperative protocol required the knee to be cast for at least a month to make sure it healed and stabilized. That, however, caused stiffness and atrophy and severely diminished range of motion, which never completely returned for many athletes.

"I was in that boat," said Frazier, who was in a cast for six weeks after surgery. "I got real stiff."

That side effect added months to the rehab timetable.

"You take [someone] out of a cast six weeks later and his leg looks like a toothpick," Sugarman said. "You take Adrian six weeks after his surgery, his quad is almost back to normal. They were at such a disadvantage that way."

Fischer credits Indianapolis-based Dr. Donald Shelbourne for revolutionizing ACL surgery and rehab protocol in the early 1990s. Shelbourne determined that an aggressive approach could accelerate the rehab timetable without jeopardizing the graft, according to Fischer.

"That was an observation that grew into what we have now," Fischer said.

Learning to wait

Now, rehab begins immediately after surgery. The goal is to improve range of motion and build strength in the knee while healing takes place. Doctors now also allow some lag time between injury and surgery -- typically a week to two weeks -- to let swelling subside and the knee to "calm down," said Moira Novak, the Gophers' director of athletic medicine who is overseeing Mbakwe's rehab.

"It used to be that a kid would tear an ACL on Saturday and we'd have him in Monday morning doing surgery," Novak said. "What we're finding is, even though you may have done surgery two weeks earlier than the next guy, the post-op response is a better response if you wait it out. At the moment it's injured, it's a very angry knee. It does not want to be assaulted again with surgery."

Rehab protocol is more layered and aggressive now, but athletic trainers caution that every individual is different, their timetables largely dependent on the scope of damage. For example, Peterson also tore his medial collateral ligament in addition to his ACL. Rubio suffered a torn ACL and lateral collateral ligament.

Mbakwe tore his ACL, MCL and suffered some articular cartilage damage that required a microfracture procedure.

"In terms of what we're doing with [Mbakwe] at the five-month mark versus what I would be doing with a person at five months with an uncomplicated ACL tear, it's different for sure," Novak said. "The earlier phase of his rehab was much slower."

Sugarman said athletic trainers "press the envelope" in their rehab approach, but they also realize there's a limit to the physical demands on the knee. The graft actually weakens around three to four months and becomes susceptible to reinjury if pushed too hard too soon.

"As an athletic trainer that's the scariest time because you know you're at your biggest risk," Sugarman said. "In my opinion, I don't think it's safe to put a guy out there before six months. It's too much stress. The body has to heal."

Time to heal

An occasional outlier patient will trim that timetable, but it's not recommended, even for elite athletes. Doctors have improved their understanding of biomechanics and the importance of proprioception (balance), but they haven't discovered a way to make the body heal faster.

"We hold our breath if somebody is going back out there in less than six months because of the biologic maturation process necessary," said noted surgeon Dr. Neal ElAttrache, who performed Tom Brady's reconstructive surgery. "So far, we've been able to really improve the technique, the actual anatomic placement of the graft to mimic the normal ACL. And we've been very good at regaining range of motion, strength and endurance."

Those advancements have prolonged careers and allowed athletes to return to action sooner. Of course, it's also beneficial, doctors note, if a patient possesses a genetic makeup in the highest percentile.

"We're operating on superior creatures physically," ElAttrache said. "It certainly helps a surgeon when you're operating on that kind of a canvas."