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- Mechanical instability of membranes — Laboratoire de Physique ENS de Lyon - UMR
- Chronic Ankle Instability Risk Identification
These symptoms were present at two weeks, 6 months and one year following the injury   .
Gait Deficits : Individuals exhibited a reduction of push off tendencies manifested as decreased hip extension and increased ankle displacement in the frontal plane during the gait analysis task   . Deficits in Jumping and Landing Tasks: During landing and jumping tests the following were reported: bilateral increases in hip flexion before initial contact preparation for landing , reduction in hip flexor moment after initial contact, hip stiffness and bilateral increased extension moments during landing, and inter-limb asymmetries. The increased asymmetry reflects the tendency to off-load the injured limb and shift the load to the non-injured side, this may explain the high susceptibility of contralateral injury      .
These deficits were evident at both acute and subacute phases and were then reported in those diagnosed with CAI. This refer to the hypothesis that these deficits are contributing to the development of Chronic Ankle Instability. However, it is still unknown whether these deficits are the reason behind the injury in the first place or they have developed as a result of the injury. Future studies needed to identify LAS risk factors with a follow-up design that allow us to relate these risk factors to the development of CAI or the contribution to recovery.
Based on Doherty et al studies   , clinicians can predict the development of CAI during acute and sub-acute phases following first-time ankle sprain if the following were present  :.
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These tasks successfully predicted the development of CAI by The reported sensitivity and specificity of these tests were CAI prevention is important, because this condition is common among athletes and less active people and could lead to major limitations and affect their performance.
The prevention strategies that will be discussed here are based on four pillars  :.
The mechanism of ankle sprain injury results in disruption of the ligamentous integrity of the structures preventing excessive inversion and supination the lateral joint capsule of the ankle and the ligaments supporting the lateral talocrural, subtalar, and distal and proximal tibiofibular joints. Either hypomobility or hypermobility of one or more of these joints will consequently develop. Hypermobility , ligamentous laxity or mechanical instability is characterized by increased joint play motion resulting in abnormal movement patterns on the instantaneous axis of rotation IAR of the joint with physiologic movement.
The underlying reason for the increased laxity after ligament sprain or tear is that the healing process wasn't optimal enough to restore the original tension leading to altered proprioceptive input from tissues that are abnormally stressed and forces the needs for compensatory motor patterns. The observed over pronation or unstable mortise are the results of ligamentous damage . Two ligamentous structures were described as the cruciates of the subtalar joint; the cervical and interosseous ligaments .
These two ligaments are believed to be damaged in ankle sprain and the residual laxity following the injury suggests damage of these structures. Since their function is to limit end-range pronation and supination, early loading of injured cervical and interosseous ligaments may compromise the healing process and cause the ligaments to heal in a lengthened position.
Therefore, many clinicians recommend constraining pronation by an orthotic device after ankle injury  to allow repair at a more optimal length.
Mechanical instability of membranes — Laboratoire de Physique ENS de Lyon - UMR
Hypomobility , on the other hand, can lead to joint instability through altering the kinetic chain of the lower extremity following LAS. Either physiologic or accessory, hypomobility causes changes in movement patterns leading to abnormal stresses and disrupted proprioceptive input. It is possible to observe hypomobility at the subtalar joint, talocrural joint, distal tibiofibular joint or proximal tibiofibular joint. Limited dorsiflexion is common following LAS, many rehabilitation approaches combine mobilization with movement and ROM exercises to restore ankle dorsiflexion.
However, accessory motion might be limited but physiological movement is restored via compensatory mechanisms from adjacent structures, for example a vertical limp during gait can be obtained to maintain forward movement of the lower limb when DF is limited at the talocrural joint. If remained in this position, the torn anterior talofibular ligament heals in an elongated position and loses the mechanical integrity that restrains the anterior displacement of the talus. Limited posterior glide is the end product limited dorsiflexion.
Both hypo and hypermobility should be evaluated and assessed in patients following LAS and those prone to develop CAI and strategies to address both conditions should be integrated in the rehabilitation. The state of function doesn't necessarily reflect optimal healing at the ankle joint complex following LAS. Therefore, treatment shouldn't be accelerated by the rehab team. Monitoring the load on the affected structures and watching signs of inflammation, helps in preventing overload and abnormal tissue stress.
To prevent consequent CAI, joint stability strategies should be adopted in rehab as well as normalized joint mechanics followed by gradual increase of load. A rehabilitation program designed to tackle the effects of injury on the ankle joint complex may offer promising results in regards with preventing CAI . The content on or accessible through Physiopedia is for informational purposes only. Physiopedia is not a substitute for professional advice or expert medical services from a qualified healthcare provider.
Chronic Ankle Instability Risk Identification
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