Clinical decision making in running form interventions: implications for injury
Clinical Decision Making in Running Form Interventions Initially written for Medbridge Education
The purpose of this article is to highlight the clinical decision making process during kinematic running analyses - focusing on evaluating the kinematic risk factors for running injury and not kinetics.
Both predictive and correlational research attempts to identify kinematic variables that are associated with an individual’s future or current injury. Many of those being:
-higher levels of pronation or pronation velocity
-increased tibial internal rotation
-increased knee abduction
-increased hip abduction or hip internal rotation
All of the above variables have been either documented as being elevated in runners with injury (correlated) or have been found to be precede the onset of injury (longitudinal research). As with most human function nothing is that straightforward though. To confuse us, all of the above factors have also been shown to have NO relationship to injury in other studies. We now have this dueling evidence base where it is very easy to cherry pick research supporting our ideas.
Pain and injury are multifactorial – simply suggesting that an injury is due to altered kinematics ignores the wealth of research highlighting the many variables that influence the pain experience. Thus, our clinical decision making is never as simple as finding a “flaw” and assuming that that is the driver of the injury. So how can we view these “flaws”?
Kinematic flaws and how we interpret them can be divided into three categories:
- Defect: the kinematic flaw is a deficit in function leading to a future injury or pain
- Defense: the kinematic flaw is not a flaw but is only correlated with the injury. The altered movement itself may be driven by nociception and is a consequence of the injury or pain. The kinematics may be driven by protective motor output
- Red herring: the flaw is not a flaw but merely an expression of the large amount of functional variability that exists across people. The flaw preceded the injury and will remain even with changes in pain.
Injury is the failure to adapt stress
To determine the significance of a kinematic flaw a few assumptions regarding the nature of injury and pain are necessary. These are naturally open to debate. First, injury and pain should not be conflated. Runner’s can have tissue anomalies that many might view as pain (e.g knee OA, hip labral tears) and have no pain. They can also have pain with no evidence of disruption in connective tissue. Pain can be viewed as the brain’s response to the perception of a threat. With many factors (cognitions, past experiences, expectations, emotions) influencing the brain’s decision to output pain – nociception created by mechanical deformation of nervous tissue being just one.
With runner’s all of these factors can be viewed as stressors inputted into the system. An ideally adapting system (at least for those who want to run pain free) would be one where the brain does not output pain. Pain occurs when some immeasurable threshold is reached where the brain perceives a sufficient enough threat to output pain. An injury can be viewed as the body’s failure to adapt to the imposed loads that exceed the threshold for positive tissue adaptability. It is assumed that both the body and brain have the ability to positively adapt to imposed demands or loads. It assumes with appropriate and graded loading that both our connective tissue strength and our pain thresholds can be improved. Injury-free and pain-free running require us to stay below these thresholds.
How kinematics might contribute to pain
Altered kinematics may either create an initial noxious event leading to nociception, may contribute to nociception by continuing to sensitize nervous tissue or may even indicate a movement habit that a runner has fallen into and nociception itself does not need to be present. This habit of movement may even, to quote Lorimer Moseley, “facilitate protective neurotags”. What might initially have been a movement flaw that helped the system (e.g a defense) has now become associated with pain that has no further value. Our conundrum as clinicians is not determining whether the altered kinematic is cause or consequence of pain but rather determining if there is value in trying to address it.
How and when to address Kinematic Flaws
After we perform a running analysis we might find a number of kinematic variables that might be related to injury. The flaws we see pose two questions:
- Can the kinematic flaw be reasonably linked to the runner’s pain or injury?
Going back to the assumption that injury or pain may occur when the demands on the body exceed its ability to adapt can we suggest that the kinematics measured might load the area of injury to such an extent that mechanical pain would occur? If a patient presents with medial leg pain, appears to pronate a great deal and the speed of that pronation appears elevated we might be able to suggest that those variables relate to the pain as biomechanical link of increased tissue strain can be made. This idea can be bolstered with post-hoc reasoning if simple interventions that might address the flaw (e.g taping an arch, running with a wider step width) positively change the pain experience. This thinking would be bolstered by some research that supports this link. But wait you naturally scream at me, there is lot of research suggesting pronation has no relevance to injury. This is absolutely true and leads us to a second question.
- What factors can mitigate or amplify the relevance of this flaw?
Rather than increased pronation and increased pronation velocity being interpreted as a defect we might argue it is merely a red herring. We see this in a number of elite runners with massive amounts of pronation and massive amounts of mileage and speed. Yet they have no pain. What factors might mitigate the proposed risk of having this assumed kinematic flaw? Could those with what appears to be a running kinematic flaw have adapted to this ‘flaw” over time? Have they progressed their mileage slowly over years? In some instances, flaws aren’t flaws. The runner is fully adapted to that gait style.
On the other hand, a novice runner may exhibit running mechanics sometimes associated with injury. She may be able to run pain free for awhile until suddenly pain develops with no change in her training. There has been no change in the loading placed on nervous tissue yet pain is experienced. A possibility exists here that the sensitivity of her system was changed. Thus her threshold for pain or injury was decreased. Since multiple factors influence this sensitivity it is important to attempt to address those factors. One such intervention would be to address the mechanics of her gait.
Strategies to address Kinematic Flaws and Pain
What’s great with treating running injuries is that we don’t always need to change the kinematic flaw. We have a number of studies showing that gait retraining can change both pain and running kinematics but we also have research suggesting that interventions can result in changes in pain with no changes in kinematics. In the latter instance, we can use the altered kinematics as a starting point in creating our therapeutic interaction.
At it’s most basic, treatment is merely the modification and judicious application of stress. The following two-step and not mutually exclusive approach can be used:
- Desensitize and Unload
- Increase tolerance to stress
Desensitize and Unload
Much of what a manual therapist does would fit into this category. Again a multifactorial approach may be necessary. Interventions may be pain physiology education, education about tissue and nervous system adaptability, taping, temporary orthotic use, gait retraining, manual therapy, movement therapies and alterations in training loads.
Increase tolerance to stress
I believe most runners can keep running. In fact, they need this stressor to adapt. If we teach runners the importance of the adaptability of their system then they will understand the importance of a graded return to activity. Gait retraining would also fall into this category but it should be remember that gait modifications primarily redistribute forces during running. Thus a slow return to running with a new style is advised to again allow for the adaptation to the different stress. Last, we can use kinematics as a window into prescribing capacity or motor control exercises. Resistance training can be justified in running injury treatment both as a pain modulator and under the idea that a tissue’s response to loading can be improved – increasing injury threshold.
A future post will elaborate on the clinical decision making of these interventions. A helpful course on understanding running biomechanics and injury can be seen in this link.
We don’t know the ideal way to run and by extension we don’t know what are true kinematic flaws in running. We know that pain and injury are multifactorial and taking this big picture view of rehabilitation is helpful. Identifying what may be kinematic flaws can still provide a window into interacting with a patient. Addressing kinematic flaws, along with a runner’s clinical presentation, through a multimodal approach (e.g. desensitization, education, gait retraining, exercise selection, activity modification) is a comprehensive approach that recognizes clinical uncertainty.