You know that saying about how a man with a hammer sees everything as a nail? That’s something those who specialize in biomechanics might want to remember when considering patients with chronic pain.
The biomechanics of an acute musculoskeletal injury are fairly straightforward, and they usually involve bones or joints being pushed past their normal range of stability. In some cases, the mechanism of injury is associated with predictable biomechanical characteristics that potentially can be altered through intervention to reduce the risk of injury occurrence or recurrence.
The pattern of pain associated with acute injury is also fairly straightforward: the injury occurs, the patient has pain, the injury heals, and the pain goes away–unless a secondary chronic condition develops.
Chronic musculoskeletal pain is a completely different animal. When that pain manifests in the lower extremities, the fact that the lower extremities are typically weight bearing and directly involved in gait suggests that the patient’s biomechanics and pain are related. But identifying the biomechanics underlying chronic pain, and altering those biomechanics in ways that relieve the pain, can be challenging.
Nobody knows this better than practitioners who treat patients with patellofemoral pain (PFP). At the past three PFP research retreats, much of the discussion has focused on the frustrations of trying to reconcile patients’ biomechanics with their pain patterns (see “Conference coverage: 3rd PFP research retreat”). Particularly vexing is that, even when interventions are designed specifically to address biomechanical variables that are known to be associated with PFP, some patients experience pain relief with those interventions while others don’t.
One possibility is that there are different subgroups of patients with PFP, each with different biomechanics, and, therefore, each subgroup will respond to a different type of intervention. And certainly there is some preliminary evidence to support this theory.
But there is also evidence suggesting there is more to chronic pain than biomechanics. That’s why the most valuable contributions to the most recent PFP research retreat might have come from keynote speaker Paul Hodges, PhD, MedDr(Neurosci), DSc, BPhty(Hons), an expert in chronic musculoskeletal pain.
Essentially, Hodges explained, how a patient experiences chronic pain and how the body compensates for that pain often make little sense biomechanically. Factors that cause pain after a year or several years may not be at all related to the factors that originally caused the pain. Pain intensity may not be at all related to degree of structural damage. Compensatory movements may relieve pain in the short term but not in the long term.
These observations cast chronic musculoskeletal pain in a whole new light—and not just with regard to PFP. Think of all the patients with chronic conditions in the foot, ankle, knee, and hip who don’t respond to biomechanical interventions, or who experience pain relief after an intervention without any apparent biomechanical change.
Biomechanics can be an excellent hammer, but some chronic conditions will require different tools. Make sure there are a few to choose from in your toolbox.