In the clinic we see it pretty often, the chronic ankle sprainer. Someone who comes in because they have sprained their ankle for the 3rd, 4th, 5th time. Or someone who has a history of chronic ankle sprains and is now presenting with knee, hip, or back pain on the same (or opposite) side.
This week’s blog post is a follow up to our post, “Harmless ankle sprain?” In that post we reviewed and discussed the mechanisms behind chronic ankle instability. As we discussed it is altered proprioception, the body’s awareness of joint position in space, that effects feedback and feedforward mechanisms resulting in an elevated chance of spraining the ankle again.
Traditionally it has been thought that the tissue damage to ligaments and tendons as a result of an ankle sprain has concurrently damaged the mechanoreceptors in those associated tissues. Mechanoreceptors are sensory organs thought to be responsible for generating the majority of proprioceptive input. So, if the mechanoreceptors are damaged, it would lead to altered proprioception and an increased likelihood of having another ankle sprain. This makes sense, except that the research on proprioceptive deficits following ankle sprain remain inconclusive. Some studies have shown deficits, while others have not. This means that there is likely proprioceptive input occurring by means beyond ligament, joint, and tendon receptors.
The updated view of joint proprioception is that proprioception is comprised of a network of tissues and receptors. The change in tension through this network of tissues (muscles, joint capsule, ligaments) during certain movements results in proprioception. In this updated view of proprioception, as the authors suggest, passive joint stiffness is likely important in the transmission of forces during movements and therefore important in the activation of proprioceptors.
The study’s purpose was to determine what the effect of an ankle sprain had on motion perception (proprioception) and passive ankle stiffness. Motion perception was measured by hooking participants up to a machine that slowly moved their ankle. Participants were asked to press a button as soon as they perceived ankle motion. Passive ankle stiffness was measured by hooking participants up to the same machine and asking them to press a button when they began to perceive a stretch sensation. The authors expected that the group of individuals with history of an ankle sprain would have worse motion perception and worse passive ankle stiffness.
The results of the study confirmed that individuals with history of an ankle sprain have a worse sense of motion perception, or proprioception, than individuals with no history of an ankle sprain. The surprise was that no significant difference in passive ankle stiffness was noted between those with a history of an ankle sprain and those without. However, the results did show that individuals with greater passive ankle stiffness had a greater sense of motion perception. This does suggest that there is a relationship between ankle stability and heightened proprioception.
In the blog post “Harmless ankle sprain?” we suggested balance exercises as a means for improving feedforward and feedback mechanisms in individuals with a history of chronic ankle sprains. It is also important to consider that altering the length-tension relationship of muscles surrounding the ankle joint may improve motion perception following ankle sprain. Physical therapists have the means to do this through traditional strengthening exercises. This may also mean that people with a history of chronic ankle sprains might consider avoiding over-stretching muscles around the ankle as this may have a negative effect on proprioception.
Marinho HVR et al. Influence of passive joint stiffness on proprioceptive acuity in individuals with functional instability of the ankle. Journal of Orthopaedic & Sports Physical Therapy. 47(12); 899-905.