The Journal of Orthopaedic and Sports Physical Therapy just released an issue specifically focusing on the knee. One of the main themes was ligament rehabilitation. They posted some grim statistics from a recent meta-analysis that only 63% of ACL repairs continue on to their pre-injury level of function and that only 44% of these athletes go on to become competitive again. They also quote that the odds of reinjuring the same knee or the opposite knee after surgery range from 3% to 49%. That doesn’t seem too good.
This issue had a few really good take home points though. They spoke about the use of open chain vs closed chain exercises. In close chain exercises for the knee, the knee joint moves while the foot is kept fixed to the floor. A good example of a closed chain exercise for the knee is a squat. In an open chain exercise the foot is not fixed to the floor and while the knee joint moves the foot swings freely. A good example here is a seated knee extension, or a quad extension.
An open chain seated knee extension places large stresses on the ACL. The more weight you add, the more stress the ACL gets. In a closed chain exercise like the squat the ACL gets no force placed upon it when squatting down to 90 degrees. (This occurs because the hamstrings are active in closed chain exercises and and counterbalance the force of the quadriceps, a lesson for another day.) What’s even more interesting is that when the resistance is increased the stress on the ACL does NOT increase. This should get some light bulbs going off in people’s minds. They also go on to recommend that lunge variations are as safe as squatting variations for ACL health.
A final few recommendations they have for ACL rehablitation are:
- Not allowing the knees to travel much past the toe during closed chain exercises
- Having a 30-40 degree trunk lean during squatting and lunging exercises to decrease stress on the ACL
- When squatting below 90 degrees of knee flexion there are some forces on the ACL. Deep squats don’t seem as safe as squats to 90 degrees.
- Strengthening the hip abductors and external rotators to normalize motion at the knee during activity.
- Promoting the heel being down and hips back during closed chain exercises
- If you must use open-chain knee extension, work in a range of 90 to 45 degrees of knee flexion because stress on the ACL is smallest in this range. Stresses are highest between 10 and 30 degrees of knee flexion.
- Progress slowly with plyometric activities as these do place stress on the ACL.
Given the high likelihood of re-injury in this population, patients, coaches and fitness professionals need to understand this stuff. Physical Therapists can only do so much in the short period of time insurance reimbursement allows them to get these athletes back on their feet. Coaches and fitness professionals need to be able to bridge the gap between an athlete coming fresh out of physical therapy and back to competitive play. I personally believe this gap is pretty large and is not being adequately addressed before athletes are back on the field playing safely. We should be able to decrease the reoccurence of injury in these athletes. So what information can the coach take away from a sciency journal article like this?
- Strengthen these athletes with closed-chain exercises such as squats, deadlifts and lunges
- Focus on the athletes keeping a flat heel, forward trunk lean(with a neutral spine) and a knee back behind the toe during these exercises.
- Don’t squat beyond 90 degrees of knee flexion in these athletes. Deadlift variations may be a safer choice in this population.
- Focus on strengthening the hip abductors, external rotators and extensors using exercises like:
- Monster walks
- Single leg glute bridges
- Single leg balance drills like bowler squats
- Focus on hip dominant movement. We know less stress is placed on the ACL with a forward trunk lean. This position places less stress on the knee and more on the hips, a stronger joint with more stability. You can really hammer this position during change of direction and acceleration drills.
- Slowly Progress Plyometrics
As with any athlete screen and find any movement dysfunction or deficiencies. Common sources of knee problems are: quad-dominant movement patterns, weak hips/core, ankle mobility problems, or foot weakness. These areas must be addressed and could have been a main culprit for how the athlete was injured in the first place. If you’re struggling to figure out what the athlete’s main problems are try giving their physical therapist a call. In my experience they love hearing from coaches and are more then happy to lend a hand. A little communication goes a long way for the athlete’s health and safety.
In conclusion, with some proper education and some planned programming I think we can get our athletes back to the field of play and decrease their likelihood of reinjury. It’s a shame to see a great athlete sidelined by an ACL tear and then get back on the field only to see them get injured again.