By Elliott Perkins
As we have discussed before in our many articles on pain, it is possible to have pain in the presence of an injury, as well as in the absence of any tissue damage whatsoever. In both scenarios, pain is a means by which our body is bringing attention to the affected area, as it is often either acutely or chronically being overloaded beyond the local tissue tolerance. This is, of course, also the case in the knee. One can tear their ACL with an acute load which exceeds the tissues tolerance, or one can develop Patellofemoral Pain (PFP); a poorly defined, often atraumatic anterior knee pain localized to the retro and/or peripatellar region of the knee (1). In this article, I talk about practical means of load management, as it is an essential component of any rehabilitation plan. Here we will discuss knee biomechanics, valgus, and simple management concepts.
Let’s make a ruckus.
Biomechanics: The Basics
Any area of study that people do PhD’s in is obviously too complex for me to discuss in entirety in a blog post. Let’s keep it simple and stick to the topic at hand.
The knee is a modified hinge joint, with most of its movement in flexion and extension, with some internal and external rotation. Since nobody ever says, “don’t let your knee straighten or else you’ll blow your everything out”, lets just talk about knee valgus.
Put your pitchforks away. Knee valgus is poorly understood, and often treated as the devil behind every knee injury. Not only is it a normal, often unavoidable movement (2), but trying to “fix it” is probably a waste of time. If we can understand what it is, we can understand when it matters and not lose sleep over when it doesn’t.
Valgus is, by definition, a joint position where the distal component is more lateral than the proximal part. Describing it as knee abduction isn’t particularly accurate though; since we have an MCL, the knee doesn’t really abduct much. Sure, in a structural valgus deformity we have an increased abduction angle, and this may lead to increased rates of lateral compartment knee OA (3) (which in turn, may or may not cause issues down the line…I digress). In this case what most people are talking about is dynamic valgus, which, simplistically, is relative internal rotation of the lower extremity when the foot is planted.
Dynamic valgus causes injuries?
Sort of. In the same way running causes Achilles ruptures. It’s not that the movement is inherently bad, but rather the load and the rate of loading that matters. We can think of it as a shock absorber. As our knee is placed in a situation where we need to absorb force, our knee will flex, our hip will flex, our hip and knee muscles will contract, and our knee will sometimes go into valgus. This happens extremely quickly (4). Valgus isn’t a “dysfunctional movement” (whatever the hell that means) and is not inherently bad for the knee. It is instead just another strategy for our body to disperse force. The issue here is, when the force being applied to the knee is greater than can be absorbed by knee flexion, hip flexion, the musculature, and finally, knee valgus; injury occurs. Again, this is not because the movement is bad, rather because the system was
overloaded.
What about valgus with deep squatting?
Sort of a non-issue for the most part. Some of the reasons that injury rates are low in the strength sports relative to other sports (5,6), despite putting the body under tremendous amounts of load, is that there are minimal uncontrolled dynamic loads being thrown at the athlete (unless someone gets tackled in the squat rack) and, typically, training volume and intensity are closely controlled. When the knee is loaded progressively and given time for the tissues to adapt, injuries don’t tend to happen much. Sure, a powerlifter may be forced into excessive valgus when failing a max lift, but this is a rare occurrence and not a regular part of squatting. In addition, ACLs tend to tear when the knee is forced into valgus with less than 30 degrees of flexion (9). This is more often seen with planting, cutting and pivoting in field sports, and not so much in strength training. Also, since knee flexion is such a good way to absorb force, ACL tears in the bottom of a squat are probably less likely to occur.
How do we deal with it?
Load management, progressive overload and focusing on strengthening the knee and hip as much as possible.
So, telling someone to “push their knees out” when squatting won’t prevent injury?
Probably not. The fact that the person is strength training will do more for injury risk reduction than any particular technique. The human body is adaptable. Sometimes it just need time to figure things out.
So how do we prevent the injuries from happening?
The only way to prevent injuries from happening is to never get out of bed. We can’t prevent injuries in sports/life, because sometimes shit happens. But we can reduce the risk of injury occurring by increasing the strength of the entire system and increasing our tolerance to load. As with most forms of rehabilitation, avoidance is not the answer. Telling someone to never allow their knee to go into valgus is like telling someone never to walk because sometimes people get knee pain if they do it too much. Its overly simplistic, reductionist and only makes sense if that person is secretly a car. Unlike a car, the human body is adaptable, responds to loads placed upon it, and doesn’t just “wear out” after a while. The structures of the knee will adapt just like any other tissue. In fact, the ACL has been seen to hypertrophy in athletes throughout a soccer season, and with weightlifting (7,8). Stronger tissues don’t break as easily. So, LOAD IT. Get it stronger. Good things will happen.
What about Patellofemoral Pain?
We can address PFP with the same principles, just applied in a different context. Similarly, just as dynamic valgus can increase load on an ACL, it also increases the load on the patellofemoral joint. But so does literally any activity So, since the person is not a car, increased load is not a bad thing. It is merely an opportunity for them to adapt and get stronger. Without an identifiable acute injury, PFP is a case where the knee joint is being overloaded and having a hard time keeping up (1). Following the strategies that I laid out in this article we modify the load on the knee to give it a chance to calm down, quit barking and build tolerance back up. The approach should be individualized, and you shouldn’t mess around with it. The research is out on whether PFP is self-limiting (10), so you don’t get the scapegoat of “it’ll get better if you leave it alone”. Other options for treatment are well laid out in this CLINICAL PRACTICE GUIDELINE (1) (seriously go read it if you haven’t, please, we beg).
What about VMO?
You can’t sit with us.
References:
1. Willy, Richard W., et al. “Patellofemoral Pain: Clinical Practice Guidelines Linked to the International Classification of Functioning, Disability and Health From the Academy of Orthopaedic Physical Therapy of the American Physical Therapy Association.” Journal of Orthopaedic & Sports Physical Therapy, vol. 49, no. 9, Sept. 2019, pp. CPG1–95. DOI.org (Crossref), doi:10.2519/jospt.2019.0302.
2. Dischiavi, Steven L., et al. “Rethinking Dynamic Knee Valgus and Its Relation to Knee Injury: Normal Movement Requiring Control, Not Avoidance.” Journal of Orthopaedic & Sports Physical Therapy, vol. 49, no. 4, Apr. 2019, pp. 216–18. DOI.org (Crossref), doi:10.2519/jospt.2019.0606.
3. Felson, David T., et al. “Valgus Malalignment Is a Risk Factor for Lateral Knee Osteoarthritis Incidence and Progression: Findings from MOST and the Osteoarthritis Initiative.” Arthritis and Rheumatism, vol. 65, no. 2, Feb. 2013, pp. 355–62. PubMed Central, doi:10.1002/art.37726.
4. Koga, Hideyuki, et al. “Mechanisms for Noncontact Anterior Cruciate Ligament Injuries: Knee Joint Kinematics in 10 Injury Situations from Female Team Handball and Basketball.” The American Journal of Sports Medicine, vol. 38, no. 11, Nov. 2010, pp. 2218–25. PubMed, doi:10.1177/0363546510373570.
5. Aasa, Ulrika, et al. “Injuries among Weightlifters and Powerlifters: A Systematic Review.” British Journal of Sports Medicine, vol. 51, no. 4, Feb. 2017, pp. 211–19. bjsm.bmj.com, doi:10.1136/bjsports-2016-096037.
6. Hootman, Jennifer M., et al. “Epidemiology of Collegiate Injuries for 15 Sports: Summary and Recommendations for Injury Prevention Initiatives.” Journal of Athletic Training, vol. 42, no. 2, 2007, pp. 311–19.
7. Grzelak, Piotr, et al. “Hypertrophied Cruciate Ligament in High Performance Weightlifters Observed in Magnetic Resonance Imaging.” International Orthopaedics, vol. 36, no. 8, Aug. 2012, pp. 1715–19. PubMed Central, doi:10.1007/s00264-012-1528-3.
8. Myrick, Karen M., et al. “Effects of Season Long Participation on ACL Volume in Female Intercollegiate Soccer Athletes.” Journal of Experimental Orthopaedics, vol. 6, Mar. 2019. PubMed Central, doi:10.1186/s40634-019-0182-8.
9. Quatman, Carmen E., et al. “Preferential Loading of the ACL Compared with the MCL during Landing: A Novel in Sim Approach Yields the Multiplanar Mechanism of Dynamic Valgus during ACL Injuries.” The American Journal of Sports Medicine, vol. 42, no. 1, Jan. 2014, pp. 177–86. PubMed, doi:10.1177/0363546513506558.
10. Rathleff, Michael S., et al. “Is Knee Pain During Adolescence a Self-Limiting Condition?: Prognosis of Patellofemoral Pain and Other Types of Knee Pain.” The American Journal of Sports Medicine, vol. 44, no. 5, May 2016, pp. 1165–71. SAGE Journals, doi:10.1177/0363546515622456.