A review of studies evaluating various therapies utilized in rehabilitation from anterior cruciate ligament reconstruction surgery provides additional support for guidelines issued by a multi-center group of 20 clinicians in 2001 (dubbed the MOON guidelines), and establishes that most have a sound basis in science.
"The therapy program favored by this group works in phases," notes Jennifer M. Weiss, MD., an orthopedic surgeon with the Southern California Permanente Medical Group at the Los Angeles Medical Center, who was not involved in the literature review.
Progression is based on meeting functional criteria, rather than the time elapsed since surgery. "The guidelines have now been use for 10 years with high success," says the study's lead author, Rick W. Wright, MD., an orthopedic surgeon at Washington University, and has been updated to "reflect incremental progress in our understanding of ACL reconstruction rehabilitation."
"This ‘protocol' is thoughtful and reasonable, and I expect that we will see it adopted with frequency by therapists and doctors far and near," said Dr. Weiss.
The goal of the current study was to conductg a brief review of the available scientific evidence for various therapies included in the MOON guidelines, and to provide the guidelines in their current form.
Continuous Passive Motion: No Long-Term Benefits
The reviewers found no long-term benefit in the scientific literature for the use of continuous passive motion (CPM) in the rehabilitation of the ACL-reconstructed knee in terms of long-term improved range of motion (ROM), and noted that the machines are "frequently difficult to approve for insurance reasons, and thus, cost becomes an issue."
Both Drs. Weiss and Cronin agreed with the study's assessment.
"For the younger population I have found no benefit to having CPM for ACL reconstruction," said Dr. Cronin, with "the majority beginning normal progression with ROM within 3-4 days after surgery." He said he would consider CPM only for an older population that has had multiple surgeries and has minimal to no physical therapy support.
For her part, Dr. Weiss felt that "machines that move the leg for the patient after surgery (continuous passive motion device) have no science to support their use."
Early Weightbearing Recommended
The MOON protocol calls for immediate full weightbearing to be initiated following ACL reconstruction. Although investigated in only 1 study (which found a significant decrease in patellofemoral pain from 35% to 8%), it continues to be a "fundamental principle that most therapists ascribe to as important in modern ACL reconstruction rehabilitation" and should be begin immediately during rehabilitation.
"Early weightbearing stimulates proprioceptive cells that provide for improved balance, muscle activation, and joint compression that are associated from a suspended, non-weightbearing leg," says Dr. Cronin. "Furthermore, early weightbearing tends to decrease hip irritation from suspending the leg and help decrease swelling through the muscular pump from quads and gastrocs."
"There is science to support immediate weight bearing," noted Dr. Weiss. "Although this is not the most comfortable thing for a patient to do after surgery, there may be benefit to the cartilage behind the kneecap."
Post-Operative Bracing Not Effective
In developing the MOON protocol, eleven studies were considered which evaluated the effectiveness of postoperative bracing involving the use of knee immobilizers or hinged knee braces (as distinguished from functional bracing for return to sport).
Because none demonstrated a clinically significant or relevant improvement in safety, range of motion including extension, or other outcome measures, and given the expense, postoperative bracing was not included as part of the original or revised MOON protocol.
This decision was reinforced by an additional six studies published since 2005, none of which demonstrated an advantage from bracing.
"The majority of ACL reconstructions function fine without a brace," says Dr. Cronin, who said he would only recommend one for an athlete who tended to be reckless, as a mental reminder to not ‘do anything dumb.'"
Home-Based Rehabilitation: Safe, But Effective?
None of the six studies evaluating home-based ACL rehabilitation, either before or after 2005, have indicated that it was deleterious when prescribed for motivated patients.
The MOON guidelines recommending 16 to 24 physical therapy visits for ACL reconstruction, said Dr. Cronin, "is consistent with my practice." While patients who are very committed to home-based programs will utilize fewer visits, Dr. Cronin's clinical experience led him to conclude that a strictly home-based program is not advisable.
"I am biased, as physical therapy is my profession," he acknowledged, "but because the goal [for athletes] is to return to high-level competition, not just simply walking or doing daily chores, care is necessary to ensure that all functional goals are met."
"As part of my protocol I have athletes return for 4 and 6 month check-ups to ensure they are progressing well. The biggest concerns that I see with rehabilitation are the ‘gray zones' between discharge from therapy and return to full competition. This is a particular concern for jumping sports like basketball and volleyball, where holding out athletes longer (not returning to play until 8-9 months as opposed to sports like baseball where 6 months is usually sufficient) is recommended," he said.
"I believe the 6 minimum visit recommended is too low but more of my athletes have been moving towards the 14-18 visit range, which is far less than the previous 35-40 visits that was standard a decade ago," Dr. Cronin stated.
For her part, Dr. Weiss said that it "turns out that motivated patients may do just as well with a home exercise program as they would with a formal supervised physical therapy program."
Open vs. Closed Chain: More Study Needed
The reviewers found few studies evaluating the effectiveness in the ACL rehabilitation process of so-called "open chain" exercises (those which tend to isolate a single muscle group and a single joint, such as leg curls and leg extensions, with or without added weight) versus "closed chain" exercises (those which work multiple joints and multiple muscle groups at once, such as, for example, a squat involves the knee, hip and ankle joints, and multiple muscles groups, e.g. quads, hamstrings, hip flexors, calves and glutes, with body weight alone or with added weight).
They said that it appears that open chain activities after 6 weeks may improve strength without adversely affecting the surgical graft and/or increasing graft laxity (e.g. looseness), and that the evidence was currently insufficient to determine whether open chain knee exercises before 6 weeks postsurgery was safe. As a result, the guidelines currently limit open chain activities in the first six weeks to light-load, short-arc quadriceps exercises.
"With the ability to activate the quads with a variety of closed chained exercises effectively, and knowing that during the first 6 weeks a graft is slowly weakening until becoming integrated into its bony tunnel, I do not see any reason at this time to push with open chained exercises," says Dr. Cronin.
"In my practice I will have athletes do light 3-5 pound open chain quads exercises from 90 to 70 degrees and 10 degrees to full extension to activate VMO but otherwise nothing heavy. Making sure the graft becomes fully integrated is the most important part of early stage rehabilitation," he says.
Neuromuscular Electrical Stimulation: Discretionary
Many studies have evaluated neuromuscular electrical stimulation in the ACL-reconstructed population, the reviewers noted, but lack of standardization and homogeneity among the studies hampered comparisons. They noted that some handheld devices were too weak to provide stimulation sufficient to lead to improved outcomes, and recommended that rehabilitation specialists "ensure that portable stimulators are capable of adequately recruiting the target muscle, or they should use a clinical stimulator in an outpatient setting." Given these uncertainties, the therapy was not included as a requirement for the MOON ACL reconstruction rehabilitation protocol, leaving it to the discretion of the individual physical therapist.
"Neuromuscular electronic stimulation (TENS unit) may help some patients, but most patients can find their strength without the use of this machine," said Dr. Weiss.
The MOON guidelines are based on a functional criterion that typically has patients ready to begin a return to sports at 5 to 6 months. The reviewers noted that two randomized trials evaluated accelerated rehabilitation, but neither found that rehabilitation dramatically lessened below 6 months, and said the "question remains whether patients can rehabilitate from this surgery and be ready to return to sports at less than 4 months." Additional research will be necessary, they said, "to prove that shorter time frames are safe for the graft, menisci, articular cartilage, and in the patient in general."
Dr. Cronin said that accelerated rehabilitation earlier than 6 months is not recommended and, even with return-to-play guidelines, it should be seen as multi-factorial and not just a matter of time. The risks associated with returning to soon and stretching/injuring an ACL graft is higher before 6 months."
He noted that research presented by two orthopedic surgeons at an annual soccer symposium reported that 90-95% of athletes return to full competition after an ACL reconstruction, but that the number drops to 40% following the second, and to 15% after the third.
"Rushing athletes back too soon puts their future in sports at higher risk than should be considered tolerable. All situations should be dealt with on an individual basis and be left to the attending medical team to decide. As a general rule he recommends to parents and coaches looking for a rehabilitating athlete to return early that they "don't erroneously hold on to the belief that the athlete is ‘the exception to the rule.' If they are, let the doctors, PTs, and athletic trainers decide."
Dr. Weiss says that "current return to sports is safe for many patients after 6 months, if they work hard with their strengthening program, but that [an earlier] return to sports has not been shown to be safe, as of now."
Neuromuscular Training: Safe and Effective
The reviewers note that 9 randomized trials evaluating neuromuscular training - including ‘proprioceptive' and balance training, perturbation training, and vibratory stimulation as part of ACL reconstruction rehabilitation - had been conducted since the MOON guidelines were issued in 2005. Because all demonstrated safety with some efficacy in their use, neuromuscular training continues to be included as part of the protocol.
Dr. Cronin says he will have an athlete on a balance board, with upper body support for safety, at 2 weeks post-surgery. "I am huge proponent of engaging the stabilization mechanisms in the body. The ACL is a proprioceptor in the knee, and following injury, no longer provides the information it once did. It is important for other structures to be maximally stimulated to help protect the ACL going forward."
The reviewers noted that a variety of randomized trials had evaluated several miscellaneous therapies:
- Aquatic training was deemed safe and effective in one study
- Slide board work was found safe and to improve quadriceps strength. (Dr. Cronin said he loved the slide board, but noted that it was expensive and that most clinics don't have them)
- Stair Master: was found as effective and safe as stationary cycling, but, Dr. Cronin counseled caution because of a concern that it might aggravate patellar tendonitis, so he uses this therapy less with patients who have undergone patellar tendon grafts.
"This group of clinicians (doctors, therapists, and athletic trainers) should be applauded for the work they are doing. With over 20 centers working together to study their patients who have torn their anterior cruciate ligament and undergone surgery, the amount of knowledge gained with this collaboration [has been] astounding," concludes Dr. Weiss.
For a full copy of the MOON guidelines, click here.
1. Wright RW, Haas AK, Anderson J, et al. Anterior Cruciate Reconstruction Rehabilitation: MOON Guidelines. Sports Health: A Multidisciplinary Approach. 2014; DOI; 10.1177/1941738113517855. (published online ahead of print January 17, 2014).