The first week of rehabilitation in an ACL reconstruction is the most important time frame.
"It sets the tone for everything else," said Kevin Wilk, one of the top physical therapists in the country who has worked with some of the biggest names in sports, including the Vikings' Adrian Peterson. "It's critical."
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Decades ago patients would be in a cast or brace for six weeks post-surgery with their leg slightly bent. Now the key seems to be straightening the knee to full extension as early as possible. With Peterson, Wilk said, he was able to do straight leg raises the day after his surgery.
By the second or third week, patients are riding an exercise bike and doing some walking and maybe even very light running in a water-submerged treadmill. That lasts for a few weeks until the athlete is about two months out of surgery.
"This is when people start to get rambunctious," Wilk said. "They're feeling good, the leg is good as far as stability, and they wonder why they can't do more than what they're doing. That's usually around the eight-week mark. And that goes for pro athletes as well as the average weekend warrior."
This is also the time when the ACL graft -- the new tissue, usually harvested from the patella tendon and connected to the femur and tibia to replace the torn anterior cruciate ligament -- is at its weakest. Between the date of surgery and eight weeks out, Wilk said, the graft will lose about 50 percent of its strength. It has to redevelop blood flow, which takes time. "We have to cool them for the next two to four weeks and gradually ramp them up,'' he said.
Swelling in the joint after activity is the most common setback, and when it occurs the patient is reeled in.
The rehab exercises actually have very little to do with the knee itself. Instead, it focuses on the muscles around the knee. The quadriceps in particular become deflated after surgery and the other large muscles in the leg, including the hamstring, and even those in the hip, must be built back up. James Andrews, the orthopedic surgeon, said that for every day of atrophy in the muscles of the leg, it takes an extra week of rehab to recover.
There are no universally acknowledged objective guidelines for moving a patient through the rehabilitation process. "It's pure guesswork,'' Andrews said. "Sometimes we guess wrong.''
Andrews, Wilk and others are working to develop objective tests that patients can attempt and pass or fail as they travel the road of rehabilitation. "Those things,'' Andrews said, "are still evolving.''
Generally, though, a patient will be able to run on solid ground without mechanical aid between 12 and 14 weeks after surgery. Every drill is added slowly, first at about 50 percent intensity and then 60-75 percent until finally it is performed at 100 percent. When that occurs varies from patient to patient. Every recovery is a test group of one. If a patient has stuck to the schedule provided by Wilk, though, it should take seven months and one week for a complete recovery. That rarely happens.
"Really they're ready when they're ready,'' Wilk said. "We assess and adjust. We're not cooking from a recipe here. We're cooking from taste.''