Changing Biomechanics: Is it necessary to change pain?

[AJ Lievre]

Why Do Patients Get Better? What Needs to Change for Them to Have Less Pain and Function Better?

Now that we have discussed biomechanics and knee pathology it is important to recognize that biomechanics only have associations with pathology. Ie runners with PFPS (especially female runners) seem to have increased hip adduction and knee valgus during running compared to those who do not have PFPS (Neal et al., 2019). However, there is no evidence (I’m aawre of) currently where increased hip adduction during running causes PFPS.

Theoretically, it would make sense that if we could alter the biomechanics of the knee (or any joint) that we could alter the stresses at the PFJ or the tib-fem joint, and in turn decrease pain and improve function. However, we really do not know what the risk factors for pain are and what mediates pain. For example, we know that smoking is a risk factor for heart disease, and if you stop smoking or never smoke you dramatically decrease your risk of heart disease. In most instances, we cannot say that for pain. We often do not know what needs to change (the mediating variable) for people to have less pain and improved function. Check out this link for a nice description and illustrations of mediating and moderating variables. https://www.scribbr.com/methodology/mediator-vs-moderator/

Here are some examples:

Female runners with PFPS appear to have increased hip adduction during running compared to others without PFPS. If decreased hip IR or adduction was the mediating variable, then patients would not get better (run with less pain) unless PT was able to decrease the kinematics with running. However, this is not the case. Exercises and education can be prescribed to try and decrease the IR or adduction, and patients do get better. BUT, for those who get better, some adduction angles improve and some do not (Earl and Hoch, 2011). Similar results were found by Baldon et al. (2014) where kinematics changed at the knee during a single limb hop test after trunk and hip strength training (compared to knee strength training), but between-group differences in pain were not significantly different.

Increased PF compressive forces are thought to contribute to PFPS due to the subchondral bone’s high volume of nociceptive receptors. If PFJ compressive forces were the mediating variable then patients would not get better unless PT was able to decrease those forces. If the load remains constant, to change the PFJ compressive forces you must alter PFJ kinematics. In Clifford et al’s (2020) study, they used 2 different types of taping techniques to alter kinematics and improve pain with functional CKC movements. Pain and function improved in both taping groups compared to the control group. However, changes in kinematics were not observed in either taping technique. So why did they get better?
Changing foot mechanics by decreasing pronation (in those we think pronate too much) or improving hip abduction/ER strength (in those we think have weakness) in theory should help to control frontal and transverse plane motion during activity thus changing kinematics and PFJ stresses. We could use orthotics to limit pronation (independent variable) to decrease pain (dependent variable), with the mediating variable being a decrease in pronation. Or we could strength train the lateral hip muscles (independent variable) to decrease pain (dependent variable), with the mediating variable being an increase in strength. In Matthew et al.s (2020) study, they compared foot orthotics to hip strength training in patients with PFPS. What they found was no difference in outcomes between those 2 groups (they both got better). However, the interesting findings were in the details.
There were 2 groups that got orthotics, 1 group that demonstrated a lot of pronation, and 1 group that had “normal” foot mechanics. Both groups got better with no difference between the groups regarding outcomes. Why would orthotics work for those who demonstrate “normal” foot mechanics if limiting pronation is the mediating variable?
The group that received strength training of the lateral hip muscles showed just as much improvement as the orthotics group. However, they did not demonstrate a significant improvement in strength. If the mediating variable is improved strength, why did these patients get better? Why did treating the hip with strength training lead to similar improvements as placing an orthotic in someone’s shoe?
Additionally, it appears that improving the strength of the lateral hip muscles does not always lead to change in kinematics at the knee (Miera et al., 2011). So do we need to improve strength or just work on strength training?
What are your thoughts on this discussion?

Consider these questions below for the discussion:

From your clinical experience, discuss when you felt that changing a patient’s biomechanics was needed for them to recover or perform a task pain-free.

Was there any evidence to back up this assertion or was this just conjecture based on your own beliefs and biases?
How was this explained to the patient? Looking back on it, do you think that was problematic? Why or why not?
What are some of your other thoughts, biases, or preconceived notions about biomechanics and pain in other regions of the body? Do they have merit?

The articles below may help to put this discussion topic into perspective. Please take the time to read one of the articles about PFPS (although I would recommend them all as they are very short). What are your takeaways and how might you apply this to clinical decisions in the future?

Crossley, K. M., & Cowan, S. M. (2019). Vastus medialis obliquus (VMO) retraining or graduated loading programme for patellofemoral pain: Different paradigm with similar results? British Journal of Sports Medicine, 53(15), 917.
Rabelo, N. D. D. A., & Lucareli, P. R. G. (2018). Do hip muscle weakness and dynamic knee valgus matter for the clinical evaluation and decision-making process in patients with patellofemoral pain? Brazilian Journal of Physical Therapy, 22(2), 105–109
Rathleff, M. S., Graven-Nielsen, T., Hölmich, P., Winiarski, L., Krommes, K., Holden, S., & Thorborg, K. (2019). Activity Modification and Load Management of Adolescents With Patellofemoral Pain: A Prospective Intervention Study Including 151 Adolescents. The American Journal of Sports Medicine, 47(7), 1629–1637.
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[Farisshd]

One recent example I have for when I decided to approach a patient complaint with training to alter biomechanics is for a patient with greater trochanteric pain/glute med tendinopathy with a very apparent hip drop during gait.

Admittedly, I did not make this decision with a specific research article in mind, but based the decision on my clinical experience and knowledge that this condition is said to be triggered by repetitive compressive or tensile loads or poor lumbopelvic or LE mechanics. This is essentially how I described my reasoning for hip strengthening, gait training, and focus on pelvic control/stability in SL stance and gait. Looking back, in this situation I stand by it, though see where relying on intuition or general knowledge base could get tricky in situations.

In regard to the discussion above, while general strengthening may not lead to the improvements expected in the examples, the improvement in the strengthening groups may be explained by the related improvements in neuromuscular control, proprioceptive gains from the repeated exercises, and or conscious or unconscious learned pain free (or reduced) movement patterns. Does this have merit, I would think/hope so, but again no specific research to site off of hand.

Response for article below to come shortly! can’t access it from the text field.
:)

The articles below may help to put this discussion topic into perspective. Please take the time to read one of the articles about PFPS (although I would recommend them all as they are very short). What are your takeaways and how might you apply this to clinical decisions in the future?

[Farisshd]

I chose to review the 2019 article by Crossley and Cowan, which echoed one that I found when a student in my first clinical rotation. At the time I saw I has a patellofemoral referral coming for an eval, and I wanted to confirm what the evidence showed was helpful. I was surprised to see that hip strengthening alone or in combination with quad/VMO tailored training was superior to quad focus alone. I have continued to address strength imbalances in the hips with this patient population from day one.
In the same clinical I remember my CI always using the magic number 3/10 for a target VAS pain score. The patients seemed to respond well to it, with less fear avoidance and a sense of control over the therapy progression. I continued to use this idea as well, but honestly never inquired into where he got the magic number. I like idea of continuing this target/limit with progression of functional loading (for various conditions) and using it as a tool to show patients that they can respond well with progression of forces, while taking care to avoid “pain” but allow “discomfort” to discourage pain inhibition, improve self efficacy, and promote increased adherence to the HEP.

[zcanova]

A specific pathology that I have found a common mechanical fault associated with it is gluteal tendinopathy/trochanteric bursitis. The research behind this pathology suggests that increased tensile forces are applied to the hip abductors and IT band when here is a lack of lateral pelvic stability and an increased adduction/internal rotation moment at the hip. In my experience, it is common for me to altered motor control patterns with these patients and I find success in improving their ability to maintain a neutral pelvis and strengthen the appropriate hip musculature to reduce the valgus moment of the femur with closed chain loading activities. I am typically able to explain this fault to patients by discussing the findings and showing them how the activities that are aggravating to them are affected by the mechanical fault. Another way I find success in explaining the fault is by demonstrating modifications to the patients positioning of the hip and allowing them to feel the difference between resting in an adduced position versus a neutral position. I think the fact that I can show them immediately how this impacts their symptoms makes a large impact on their perceptions and understanding of the implications regarding the movement fault.

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