Extension Drives Everything: Not an Opinion

There is much debate on the best way to treat a patient who has suffered an ACL tear regarding graft choice and when to do the surgery. However, the one opinion that most agree upon is doing a reconstruction on an isolated ACL injury to all school-age athletes and those individuals who want to return to high-risk activities is appropriate. In addition, individuals with an ACL deficient knee do not require surgery if they have no desire to return to high impact sports or activities that require quick changes of direction. Either way, patients need to properly rehabilitate after an injury and prior to doing surgery or educated on how to manage the ACL deficient knee long term. The benefit of treating only knees is being able to watch the trends of those who do well and those who struggle regardless of the diagnosis of the knee joint.

One of the consistent findings in our office with all our patients, not just ACL tears, is the patients that come into the office with a flexion contracture are more dissatisfied with their knee than those that present with some degree of hyperextension to the knee. Normal knee range of motion is not a textbook number. Normal knee range of motion is motion that is equal the opposite, uninvolved knee. The average hyperextension in the knee joint is 4-5 degrees. Most knee rehabilitation programs seek to treat all the patient’s symptoms and deficits simultaneously verses addressing one deficit at a time. The most overlooked symptom with patients with a “bad” knee is the fact that there is a flexion contracture in that knee and what many fail to recognize is that even a degree or two loss of full hyperextension in the knee joint can lead to symptoms of pain and decreased function. Proper range of motion assessment with the heels propped and knees suspended is the only way to measure for a difference.

We have studied the relation between range of motion and outcomes in our patients with ACL tears, osteoarthritis and total knee arthroplasty. Early in Dr. Shelbourne’s career, he found that patients that did not get full, symmetrical hyperextension of the knee before and within the first month post op developed complications like arthrofibrosis, decreased quad strength, and increased risk of developing osteoarthritis. Through the years of changing and developing what is known as the “accelerated rehab program,” we have learned that ACL patients must get symmetrical extension prior to surgery if they are to achieve it post op, and then they have to maintain it post op to avoid the complications. We have taken these findings and applied this to all our patients, regardless of their diagnosis. We have found that even our most arthritic knee patients that improve on their extension have improved pain levels and improved function. There are very few studies that exist with greater than 20-year follow up of ACL reconstruction, and we have been collecting data prospectively since 1982. Using the IKDC (International Knee Documentation Committee), normal range of motion is extension within 2 degrees of the opposite knee; the following chart shows the subjective scores based on range of motion based on the IKDC criteria:

Of 257 patients with both normal knee extension and flexion, 44.3% had normal radiographs. Of 166 patients who had less than normal knee extension or flexion, 21.1% had normal radiographs (P value of <.001). Within this patient population, we also found that range of motion loss will significantly increase the odds of developing osteoarthritis in the long-term.

Failing to achieve normal flexion and/or extension range of motion by time of discharge increases the probability of continued loss of motion 8 to 20 times respectively at 20 years follow up.

We are finding that patients that come to us with arthritic knee(s) with or without previous injury or surgery present with stiff knee(s). Instead of signing them up for a total knee arthroplasty, we do physical therapy first with number one goal of maximizing the extension and then flexion. Even in the very stiff, arthritic knee the range of motion can improve despite the level of osteoarthritis. As the range of motion improves, so does the pain complaints and the function.

Of 396 patients that participated in a non-operative treatment study, 24% went on to have a total knee arthroplasty. Even those that have been consistent with stretches for their knee and went on to have a TKA, did better with the post op rehab as their knee(s) were much better condition prior to surgery and use to doing the exercises. At two years post op TKA, 91% have at least 0 degrees or some degree of hyperextension and the average flexion at two years post op is 123 degrees. Survey results with use of the KOOS show scores within normal range at one year. The following table shows the percent of patients’ KOOS scores at one-year post op:

The other important benefit of gaining symmetrical extension in all knees is the increased ability to gain symmetrical strength in the quads. We use an isokinetic machine to test quad strength with all of our patients. With the ACL patient population, we use 180 and 60 degree per second speeds versus the TKA patients tested at 180 and 120 degrees per second. We tend to look at the slower speeds (60 and 120 degree per second) which each group to have a better objective measurement of where their functional quad strength is side to side. The lower extremities should be within 10% of each other with typically the dominant leg being stronger. Using the IKDC criteria of normal extension being equal to or less than 2 degrees of the opposite side, we can see on the following grafts that normal extension does have an effect on getting symmetrical quad strength back. Because we emphasize symmetrical extension in all of our patient populations, we do not see very many patients post op that fall into the abnormal category. The following charts show post op ACL and TKA patient populations with quad strength at 2 months post op:

ACL population

Quadriceps strength based on extension ROM: 2 months postoperative (ACL)

TKA population

Quadriceps strength based on extension ROM: 2 months postoperative (TKA)

The other benefit to being able to treat and collect information on one problem, is that we have found with our ACL population the secondary damage to the joint from the injury has little impact on the functional outcomes, patient satisfaction and development of osteoarthritis. However, again the extension does have a great impact. The charts below demonstrate the rate of osteoarthritis based on meniscus and chondral status:

The next time you are addressing a painful knee, first consider evaluating extension in that knee and compare to the opposite side, as they should be equal when assessed passively and actively and feel the same side to side to the patient. Regardless of what else might be going on in the knee joint, this should be the first thing that is addressed.