Clinically Relevant Anatomy
Ankle sprains are a common sports injury, with approximately 20% of patients with acute ankle sprains developing chronic ankle instability . Two million lateral ankle sprains occur each year in the United States , affecting the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and/or Posterior talofibular ligament (PTFL). The literature reflects a high incidence of persistent disability and relapse.             
Following acute ankle sprains, postural control proprioceptive muscle reaction time and strength deficits are common           [ 25]              This can lead to chronic ankle instability ( CAI).   Inability to perform jumping and landing tasks within 2 weeks after first lateral ankle sprain (LAS) and poorer dynamic postural control and lower self-reported function 6 months after first LAS predicted final CAI outcome . CAI includes mechanical instability (movement Beyond normal physiological limits) and functional instability (objectively stable, subjectively perceived instability associated with sensorimotor or neuromuscular deficits).        
Clinically, the history of a patient with chronic ankle instability reveals recurrent ankle sprains and severe inversion injuries in the past. They take special precautions against strenuous activities with weight and walking on uneven surfaces.
CAI is characterized by a spectrum of deficits that can be assessed by a range of sensorimotor measures. Clearly, reflex responses to afferent somatosensory information and conscious perception of deficits in efferent motor control are associated with ankle instability . specific The origin of these deficits locally at the ankle ligaments or at the spinal or supraspinal level of motor control has not been fully elucidated. However, it is clear that both feedback and feed-forward mechanisms of motor control change with ankle instability.
The main cause of chronic ankle instability has been found to be: decreased proprioception due to loss of mechanoreceptors and decreased strength of the varus and varus muscles. When a lateral ankle sprain (LAS) occurs, damage is not only to the structural integrity of the ankle joint Various mechanoreceptors in the ligaments as well as in the capsular ligaments and tendons around the ankle joint. Together, these receptors provide feedback about joint pressure and tension, ultimately providing joint movement and a sense of position. through afferent nerve fibers that Information is integrated with the visual and vestibular sensory systems into a complex control system used to control posture and coordination. When afferent input changes after injury, proper corrective muscle contraction may be altered. mechanoreceptors Surrounding the ankle with LAS may lead to dysfunction and chronic instability after the initial injury
Proprioception has been described as the outgrowth of sensory information gathered to the central nervous system by mechanoreceptors located in the capsularis, ligaments, muscles, tendons, and skin. Trauma to ligamentous tissue containing mechanoreceptors may result in partial differentiation Proprioceptive deficits can result, and subsequently CAI. Postural control deficits are frequently reported after acute LAS and during quiet standing in patients with CAI .
In addition to sensorimotor deficits, researchers have also proposed that peroneal muscle weakness is associated with chronic ankle instability. Insufficient valgus muscle strength reduces the ability of these muscles to resist inversion and return the foot to a neutral position, preventing Reverse the sprain. Patients with chronic ankle instability have demonstrated not concentric but eccentric valgus weakness. Other researchers have shown concentric inverter strength deficits in patients with CAI. They have two explanations for the reversal weakness. first it can is a result of selective reflex inhibition of the ability of the ankle varus muscles to initiate movement in the direction of the initial injury. A second cause may be deep peroneal nerve dysfunction due to overstretching of the peroneal nerve. Another theory they speculate is that motor neurons The pool of neurons associated with valgus function became less excitable by the lateral ankle sprain, while the pool of motor neurons associated with valgus function was not affected as much.
Predictors of Chronic Ankle Instability
Doherty  proposed that combining SEBT as a predictor of homeostasis with measures of foot and ankle performance as patient self-reported outcomes could predict the likelihood of CAI.
- The Star Excursion Balance Test (SEBT) (specifically posteromedial extension) has very valuable predictive power for chronic ankle instability 
- Measures of ankle and ankle performance (particularly activities of the ADL subscale) can be used as objective measures of recovery after acute LAS. Low scores on this questionnaire, especially posterolateral extension combined with SEBT, may predict CAI.
Read more here – Chronic Ankle Instability Risk Identification
Mechanical ankle instability is caused by ligament laxity; functional ankle instability is caused by deficits in postural control, neuromuscular deficits, muscle weakness, and proprioceptive deficits. Chronic ankle instability selection criteria recently updated by the International The Ankle Consortium  may have seven subsets, including the frequency of interaction of mechanical instability and sensory instability in multiple sprains .
During the physical examination, hindfoot movement should be recorded and peroneal muscle strength tested. Signs of ligament laxity need to be checked. Stability tests such as anterior drawer and talar tilt tests should be performed. In patients with chronic ankle instability, proprioception is Often abnormal; 86% of patients with grade III ankle sprains had a peroneal nerve traction injury and 83% had a tibial nerve traction injury. To test for proprioception, a modified Romberg test can be used: the patient stands on the unaffected ankle, eyes are opened and then closed, and the Injured ankle.
MRI is most useful for chronic ankle instability. Ligament injuries can be seen as swollen discontinuities of fibers, lax or wavy ligaments, or non-visualization on MRI. The ankle should be in neutral or slight plantar flexion to help align the ATFL and CFL. Limitations of MRI are cost time availability Motion artifacts that cannot accurately predict chronic sequelae after acute injury.
- Lower Extremity Functional Scale
- Foot Function Index
- Foot and Ankle Ability Measure
- Cumberland Ankle Instability Tool
- Star Excursion Balance Test
- Y Balance Test
Management / Interventions
Distinguishing between functional and anatomic ankle instability is important to guide proper treatment. Unlike acute ankle sprains, chronic ankle instability may require surgical intervention. Non-surgical treatment is strongly recommended prior to any surgical procedure Patients with chronic ankle instability. During the rehabilitation phase, neuromuscular and proprioceptive training and orthotics (if indicated) should be provided.
Since research has shown that repetitive ankle injuries can lead to neurosensory proprioceptive and mechanical impairments, exercises that increase proprioceptive balance and functional capacity are often performed after ankle injuries in addition to strengthening muscles.
Problems found in CAI patients are decreased postural control and awareness of joint position and increased instability. Changes in the functioning of the sensorimotor system are thought to be at the root of these problems. Balance training is an important part of current rehabilitation programs For CAI. The effect of balance training on sensorimotor deficits typical of CAI has been determined, including postural control dynamic balance joint position sense and segmental spinal reflexes. The Star Excursion Balance Test Is Considered An Excellent Rehabilitation Method Balance exercise in CAI .
Isokinetic muscle strengthening has been shown to have a positive effect on functional muscle strength and proprioception in the ankle.
Docherty  recommended that patients with CAI use a brace when performing high-risk activities, such as returning to sport within 6 months of an ankle sprain. Risks such as individual needs, likelihood of dependence on cost of appropriate use should be taken into account.
Surgery may be considered when bracing and taping methods fail to provide support for chronically unstable ankles . Surgically, the injured ligament is repaired by applying a tendon graft or localized tissue. Surgical methods include the Broström procedure Mainly repairs damaged ligaments. Augmentation of the primary repair by tendon transfer protects the repair and increases stability. Arthroscopy is ready to help diagnose and treat ankle instability.
Chronic ankle instability is often associated with an injury that evolves from a contributing factor. They do not necessarily occur with chronic ankle instability, nor do all of these injuries, if any, occur at the same time. An associated pathology that may accompany chronic ankle instability is chronic localized pain Syndromes Neuropraxia Syndrome Tarsus Syndrome Tendon disorders such as peroneal tendinopathy Dislocation or subluxation Impingement syndrome Fractures such as anterior calcaneal process Fibula and lateral Talar process Loose bodies and talar dome or osteochondral distal tibia Damage .
Al-Mohrej  described the following injuries that often accompany chronic ankle instability:
Sinus Tarsi Syndrome
Sinus tarsi syndrome is common in basketball and volleyball players, dancers, and people who are overweight. It is also common in patients with flat feet and hyperpronation deformity. It involves pain and tenderness in the sinus tarsi; that is the outer side of the hindfoot. may happen After one or a series of ankle sprains. Although MRI can show evidence of inflammation, it is diagnosed by exclusion. Treatment for sinus tarsi syndrome is primary repair of the sinus tarsi ligament with tendon augmentation or both
Osteochondral defect (OCD) is damage to the talus. They may include blistering of the cartilage layer and cyst-like lesions in the bone, or even fractures of the bone layer and cartilage. One trauma or recurring trauma can lead to OCD. OCD shows swollen ankle instability and long pain. The exact mechanisms of pain and instability are not fully understood. The ideal treatment depends on the size and location of the lesion.
Peroneal tendinopathy is chronic inflammation of the peroneal tendon that causes weakness in the active ankle stabilizer. It occurs when a person irritates the tendon by performing repetitive activities for a long period of time. Also, poor and rapid training and poor shoe wear can cause fibula Tendinopathy. People with a rearfoot varus position are more likely to develop peroneal tendinopathy. Most cases of peroneal tendinopathy are managed conservatively, although surgical debridement and stimulated healing (open or tenoscopic procedures) are gaining popularity.
Subtalar instability is a morbidity of unknown etiology. It seems impossible to diagnose. It can have symptoms of chronic ankle instability. Patients with clinical subtalar instability have increased internal rotation. It is treated with tendon transfer or tenodesis Procedures such as Chrisman-Snook or by anatomical ligament reconstruction.
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