A Closer Look At Foot Orthoses For Chronic Ankle Instability
In light of an increasing body of research on the effect of orthoses on chronic ankle instability and postural sway, this author discusses essential biomechanical considerations and recommends orthotic prescriptions and modifications to treat unstable ankles.
Although clinicians use foot orthoses to treat a myriad of clinical conditions, they rarely employ these devices to treat chronic ankle instability. When they do use foot orthoses to treat chronic ankle instability, prescription strategies and the design of foot orthotic devices vary significantly among practitioners. This may reflect a lack of understanding about this enigmatic condition, which poses a challenge for even the most skilled podiatric physician.
Understanding the complexity and nuances of chronic ankle instability will provide the practitioner greater insight to understand how to implement foot orthotic therapy effectively in combination with other interventions, which can result in very favorable patient outcomes.
The ankle sprain is the most common injury in sport and accounts for more time lost from participation than any other injury.1 Almost half the patients who suffer a significant ligamentous injury to the ankle continue to suffer the long-term, serious disability known as chronic ankle instability.2 This suggests that we do not treat ankle sprains properly as our treatment protocols are failing at least 50 percent of the time.
One reason for this high failure rate is a prevailing standard of practice to return an athlete to sport too soon after an ankle sprain before adequate ligament healing has occurred. While basic science has taught us that ruptured ligaments require at least six months to repair and restore strength adequately, high school and collegiate athletes routinely return to play within weeks of this injury.3 Even in the non-athletic patient who has suffered an ankle sprain, practitioners fail to protect the injured ligaments beyond a few weeks, allowing unprotected ambulation, which dooms the patient to incomplete healing.
When ligaments fail to heal after an ankle sprain, there are long-term, if not permanent, consequences. These impairments include permanent pain, swelling and recurrent ankle sprains resulting in up to 72 percent of people having an inability to return to previous activity.4 There is a known link between chronic ankle instability and the development of osteoarthritis of the ankle.5 Researchers have reported serious quality of life consequences of chronic ankle instability such as decreased participation in exercise and withdrawing from occupational activity.6
A Closer Look At The Pathophysiology Of Chronic Ankle Instability
Unhealed ligaments do not entirely account for all of the contributing factors of chronic ankle instability. Traditionally, the literature has attributed chronic ankle instability to two potential causes: mechanical instability and functional instability.7 Functional instability may be caused by specific insufficiencies in proprioception, neuromuscular control, postural control or strength. Mechanical instability may be caused by factors that alter the mechanics of one or more joints within the ankle complex. Potential mechanical insufficiencies include pathologic laxity, impaired arthrokinematics, synovial inflammation and impingement, and degenerative changes.8 Patients with chronic ankle instability may have only mechanical instability, functional instability or a combination of these entities.