Why Open Kinetic Chain Exercises Are Not Just Safe, But Essential After ACL Reconstruction

Not only are open kinetic chain exercises after ACL reconstruction safe, they're essential for the proper development of that graft tissue. That's one of the things we talked about in the Rehab & Performance Lab podcast with Dr. Lynn Snyder-Mackler on the open kinetic chain debate. We need to change our perspective from, "Is open kinetic chain safe?" to "open kinetic chain exercise is essential after ACL reconstruction!"

Quadriceps Strength: The Undisputed King of ACL Recovery

If you want to know the number one predictor of success after ACL reconstruction, it's quadriceps strength – hands down! This isn't just about short-term recovery; it's about long-term outcomes, including reducing the risk of re-injury and osteoarthritis. As a matter of fact, longevity research even says, "If you want to live a long life, be sure you have strong quads"! That’s a strong statement from Dr. Synder-Mackler, but it’s the truth!

Functional appearance can be deceiving. Patients might look like they're doing well, but if we put them in the lab, we often see all kinds of adaptations and compensations. Why? Because they're shifting control away from the knee to the ankle and hip to achieve movement. This is why isolated quadriceps testing, ideally with tools like isokinetic dynamometry, is absolutely essential.

If you're not measuring quad strength – and that doesn't mean single leg leg press, but actual isolated quad strength – you don't know if they're getting stronger! It breaks my heart when I hear patients have been discharged at six months, not feeling ready, and then I ask if they were strength tested or if they were doing isolated knee extensions, and the answer is "no and no!" We cannot underestimate the importance of getting that quad strength back.

We even know that patients who recovered quad strength early never developed certain negative brain mapping changes that can happen after intra-articular knee injury! 

Debunking the Open Kinetic Chain Myths

For too long, there's been so much confusion around open kinetic chain (OKC) strengthening after ACL reconstruction. It feels like people have gone to one extreme or the other, saying OKC is unsafe, painful, inappropriate, or will cause graft problems. But as Dr. Snyder-Mackler so clearly puts it, to those concerns, I say: "No, no, no, and no!".

The research simply doesn't support these fears. In fact, historical concerns originated from outdated graft placement techniques, and these issues were incorrectly blamed on open-chain exercises. The good news is that the current evidence is totally in favor of open kinetic chain exercises! These myths just persist, but they're not backed by what the research says.

Embracing Strain: Essential for Graft and Tendon Healing

This is a big one for me: The absence of strain is not the goal for healing collagenous tissues like the new ACL graft or the donor tendon site! Think about it: too much strain, tissues can rupture. But too little strain, and they actually absorb. We need that sweet spot of optimal strain.

Some folks worry about OKC causing too much strain, but here's the reality: All exercise causes strain. Even just walking produces ACL strain, sometimes as much as 11-15%! And studies have shown that open chain knee extension with a weight actually produces similar strain levels (around 3.8%) as closed chain squats. The point is, controlled, purposeful strain is vital.

Why? Because tendons and ligaments, which are similar tissues in the body, don't heal properly unless they're given the right strain to help the scar tissue organize and line up along the lines of stress. If you're too conservative and don't apply stress, you can end up with a big, disorganized ball of scar tissue that's not strong. We need to apply stress for the new collagenous tissue to heal and do its job.

Rethinking Anterior Knee Pain After ACL Reconstruction

Should we be approaching anterior knee pain after ACL reconstruction differently? And I think the answer is yes. We discussed this with Dr. Lynn Snyder-Mackler in this episode. And I think the first thing we have to do is identify where that anterior knee pain is coming from. If it's coming from the patellar tendon, we probably should treat this more like a tendinopathy. And we need to be thinking about loading the tissue and even though that tissue loading may be painful, we should probably do it in a controlled manner. Remember, if we perform MOVEMENT in painful patterns we will cause compensations. But with tendinopathies we need to think about stressing the tissue in an isolated perspective: not doing it in a closed chain where we're gonna get compensations because of that pain, but rather stressing the tissue in the open chain where we're gonna get the stress and the tissue remodeling we need without the compensations of doing it during a movement. 

And if you have patellar tendon pain from the graft harvest site? Dr. Synder-Makcler uses a pain-modified tendon model. This means if your pain is 5 out of 10 or lower, you keep going! (I think that pain level might be a bit high -- see more discussion on this in the Beyond Eccentrics for Lateral Elbow Pain Podcast episode) If it's more than 5/10 pain, you modify the exercise, but you don't avoid pain altogether. Absence of pain at a tendon injury site is not the goal. A "sick tendon" needs appropriate loading to reorganize. To me, this makes an even stronger case for isolated open kinetic chain exercises, because you can get that direct loading without the compensatory patterns that come with painful closed-chain movements.

The Long Game: Why Quad Strength Matters for Life

Here’s something crucial: We tell our patients who've had these major intra-articular knee injuries that they should be doing quad strengthening exercises for the rest of their lives! That symbiosis between the quads and the knee doesn't just go away. We know that weak quads are strongly linked to osteoarthritis. Patients are already at risk for OA just from the traumatic knee injury, so maintaining strong quads is a vital protective measure!

"When quads are weak, people walk with a stiff, quasiatic gait, truncating their range of motion and leading to higher ground reaction forces. They don't push off effectively, and the weaker their quads are, the stiffer their gait." You can't break that compensation pattern if their quads aren't strong enough! The body prioritizes getting around, no matter what compensations occur. But our goal should be to give them the foundation so they can move normally, not just compensate their way through. As I always say, the fundamentals win every time!

If you would like to learn more about systematic strengthening after ACL Reconstruction and additional diagnoses throughout the body (shoulder, core, etc.) join us in the Coaches Club. Your Path of Mastery begins here.

You can listen to the episode at the links below. If you'd like CEUs, make sure to use the MedBridge link.