Editing Instability (section)

==Joint instabilities==
The most common residual disability after any sprain in the body is instability.  Mechanical instability includes insufficient stabilizing structures and mobility that exceed the physiological limits.  Functional instability involves recurrent sprains or a feeling of giving way of the injured joint.<ref>{{cite journal |last1=Guskiewicz |first1=K. M. |first2=David H. |last2=Perrin |title=Effect of Orthotics on Postural Sway Following Inversion Ankle Sprain |journal=Journal of Orthopedic and Sports Physical Therapy |volume=23 |issue=5 |pages=326–331  |date=1996 |doi=10.2519/jospt.1996.23.5.326 |pmid=8728531 |doi-access=free }}<!--|access-date=15 October 2013--></ref>  Injuries cause [[proprioceptive]] deficits and impaired postural control in the joint.  Individuals with muscular weakness, occult instability, and decreased postural control are more susceptible to injury than those with better postural control.  Instability leads to an increase in postural sway, the measurement of the time and distance a subject spends away from an ideal [[Center of pressure (terrestrial locomotion)|center of pressure]].  The measurement of a subject's postural sway can be calculated through testing center of pressure (CoP), which is defined as the vertical projection of center of mass on the ground.  Investigators have theorized that if injuries to joints cause [[deafferentation]], the interruption of sensory nerve fibers, and functional instability, then a subject's postural sway should be altered.<ref>{{cite journal |first1=A. |last1=Pintsaar |last2=Brynhildsen |first2=J. |first3=H. |last3=Tropp |title=Postural Corrections after Standardised Perturbations of Single Limb Stance: Effect of Training and Orthotic Devices in Patients with Ankle Instability |journal=[[British Journal of Sports Medicine]] |volume=30 |issue=2 |pages=151–155 |date=1996 |doi=10.1136/bjsm.30.2.151 |pmid=8799602 |pmc=1332381 }}<!--|access-date=15 October 2013--></ref> Joint stability can be enhanced by the use of an external support system, like a brace, to alter body mechanics.  The mechanical support provided by a brace provides cutaneous afferent feedback in maintaining postural control and increasing stability.