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11 Articles in Volume 10, Issue #8
A Neuro-geometric Basis for Pain Management
Brain Reorganization with Severe Pain: New Understanding and Challenges
Chronic Migraine: An Interactive Case History, Part 2
Diagnosing and Managing Chronic Ankle Instability
High Potency Ultrasound for the Treatment of Connective Tissue Disorders
Intranasal Naloxone for At-home Opioid Rescue
Misuse of ‘Hyperalgesia’ to Limit Care
Neurological Effects of Therapeutic Laser
Preventive Medications For Headache
Psychological Wounds of Trauma and Motor Vehicle Accidents
Treat the Pain... Save a Heart

Diagnosing and Managing Chronic Ankle Instability

Characterized by discomfort, swelling and tenderness; chronic ankle instability can be a result of compromised integrity of associated bones, tendons, or ligaments.

The ankle joint consists of many bones, ligaments and tendons that all play an integral part in maintaining its stability. All these function to allow a multitude of movements within the ankle joint. Consequently, ankle instability can result if any of the related bones, tendons, or ligaments are compromised. The tibia and fibula are intimately joined by the interosseous membranes. These two bones also share connections with the ligamentous complexes of the foot so that any sprain on the ligaments can also potentially cause a distal fracture in the bones of the lower leg. Additionally, the tendons from the muscles of the lower leg—mainly the Achilles tendon and the peroneus longus and brevis, are closely associated with the bones of the foot. Injury to these tendons will likely result in ankle instability.

Figure 1. The ankle is comprised of three articulating bones: tibia, fibula, and talus.1

Anatomy and Mechanics of Ankle Motion

The ankle joint has no distinct boundary due to its intimate connections with the lower leg and foot. The ankle is a synovial, hinge joint that is comprised of three articulating bones, three groups of ligaments and three supporting tendons. The bones of the lower leg are the tibia and the fibula. Their distal ends form a mortise that encompasses the talus, which is a bone in the foot (see Figure 1). The tips of the tibia and fibula surrounding the talus form the medial and lateral malleoli, respectively. An imaginary line connecting the malleoli approximates the axis around which the ankle moves during motion.

This axis acquires an oblique angle that points posteriorly and inferiorly. Because of this, plantarflexion of the ankle also produces internal rotation or inversion, while dorsiflexion causes external rotation or eversion.2

The ligaments of the ankle are best described by categorizing them into the interosseous ligamentous complex, the medial ligamentous complex and the lateral ligamentous complex (see Fig-ure 2).

Figure 2. Ligaments associated with ankle stability. Together, these ligaments work to provide stability to the ankle joint while in motion. The interosseous complex tightly binds the tibia and fibula and, at the same time, allows slight rotation of the tibia during ankle movement. The medial complex functions to limit excessive external rotation of the talus within the joint space. These ligaments are collectively referred to as the deltoid ligament. Lastly, the lateral complex, consisting of the posterior talofibular ligament (PFL), calcaneofibular ligament (CFL), and anterior talofibular ligament (AFL) serves to prevent extreme internal rotation of the talus.

The ankle joint is further supported by tendons from muscles of the lower leg. The Achilles tendon, which connects the gastrocnemius and soleus muscles to the calcaneus bone in the foot, is the most important tendon for walking, running, jumping, and standing on tiptoes. The peroneus longus and brevis tendons course just posterior to the lateral malleolus and inserts on the lateral first metatarsal and cuneiform bone of the foot. These tendons allow eversion of the sole of the foot and plantarflexion of the ankle (see Figure 3).

Mechanism of Ankle Instability

Due to the complexity of the ankle joint and surrounding structures, any injury to the bones, tendons, or ligaments can result in instability. Fractures or dislocations of the tibia or fibula can cause ankle unsteadiness. For example, axial impact on the heel of the foot—that can occur with simple actions like jumping from a higher to a lower level—will produce a vector of force directed into the distal tibia. This, in turn, can cause a pilon fracture, or a fracture of the horizontal articular surface of the tibia.3 Such an injury to the tibia causes an increase in contact stress between the tibia and talus and is an important pathomechanical factor in unstable joints.4 Additionally, the fibula may also have a profound effect on ankle stability.

Although stable ambulation can occur with a section of the fibula removed, it was found that resection of the fibula segment close to the tibiofibular joint resulted in significant ankle instability. Consequently, by resecting parts of the distal fibula, a mobile remnant is produced which causes an inability to withstand loading pressure. This instability is partially due to the compromised integrity of the interosseous membrane between the tibia and fibula.5 In a study done by Thordarson et al, it was found that displacement of the fibula by a shortening or lateral shift of two millimeters, together with five degrees or more of external rotation, increases the contact pressures in the ankle joint and causes ankle instability.6

Damage to the tendons supporting the ankle joint can also cause ankle instability. Even a simple tendonitis due to overuse of the respective muscle can produce significant unsteadiness. For example, there has been an association between a split in the peroneus brevis tendon Figure 3. Tendons from muscles of the lower leg provide additional ankle support.1and chronic ankle instability. Lateral ankle instability can cause laxity of the superior retinaculum which is a ligament that wraps around the proximal ankle joint. This laxity can cause a peroneus brevis split and, in turn, this split results in chronic ankle instability.7 Accordingly, in a study done by Kim et al, the researchers concluded that people with chronic ankle instability also possessed decreased spinal reflexes of the peroneal tendon and soleus muscle. They theorized that this altered reflex may be a potential mechanism of sensorimotor deficits that are associated with chronic ankle instability.8 Further, as the peroneal tendons are not the only tendons that traverse the ankle joint, patients with Achilles tendinopathy should also be examined for ankle instability. With a chronic Achilles tendinopathy, the area of swelling and pain moves with plantar or dorsiflexion of the ankle. This pain and swelling will further limit ankle joint mobility and increase the instability.9

Diagnosis/Etiology of Ankle Instability

When a person presents with ankle instability, the first step is to determine whether or not the injury demands emergency care. A cost-effective way to determine whether the etiology of the ankle sprain is purely ligamentous or may include bone fractures is by using the Ottawa Ankle Rules (OAR) since it has a sensitivity of over 98%.11 The OAR state that there is an increased likelihood that the ankle injury is accompanied by a fracture if the person experiences pain in the malleolar or midfoot region and meets at least one of the two criteria:

  • 1) Bony tenderness on palpation of the posterior edge of the distal 6 cm of the tibia or fibula, or tenderness on the medial or lateral malleolus.
  • 2) Inability to bear any weight on the affected foot immediately after the injury and for four steps into the emergency department.

If the OAR is satisfied, then the physician should move forward with radiographs to rule out bony fractures of the foot or lower leg. It is important to note that a plain x-ray should be the primary test of choice because magnetic resonance imaging has been shown to not be any more sensitive or accurate as a tool.12 If the OAR criteria are not met, the physician can confidently exclude fractures and opt out of using radiographs for diagnosis. However, the physician must keep in mind that serious ligamentous tears can still be present even when the OAR is not met.

With ligament injury, the lateral ligamentous complex is more prone to damage due to the anatomical security of the ankle while in dorsiflexion and eversion. Because of this, most sprains occur while the foot is plantarflexed and inverted. As an ankle sprain only signifies damage to the ligaments but does not shed light on the degree of damage, the damage is quantified as a grade. With a Grade 1 injury, the AFL is presumed to have a partial tear. Those affected are able to perform normal activity with slight pain. Grade 2 injuries encompasses partial or complete tear of the AFL and with a possible partial tear of the CFL. Those affected with a Grade 2 tear present with diffuse swelling, tenderness, and moderate functional loss. A Grade 3 injury marks a complete tear of the AFL, CFL, and PFL. It presents with significant functional loss, marked swelling and tenderness.10

Other causes of ankle instability can be due to problems with the tendon—whether it be from intrinsic tendon pathology, a result of increasing age, compromised vascular supply or extrinsic factors. Commonly, extrinsic factors occur due to overuse injury. A common tendon that is injured is the Achilles tendon. For this reason, individuals who partake in running or jumping activities are more prone to developing Achilles tendonitis—especially if they do not appropriately stretch the muscles before participating in activity.13 Various anatomical factors also play a role in the etiology of the injury including distinct characteristics of a runner’s touchdown angle and plantarflexion peak torque.14

Management of Ankle Instability

Once the diagnosis of an ankle sprain is made, conservative management is always preferred. In the early stages of a mild sprain, the RICE protocol (rest, immobilization, compression and elevation) is usually used. For first time Grade 1 and Grade 2 ankle sprains, a form of immobilization using a combination of an elastic wrap and air-stirrup ankle brace provides the ability to walk and climb stairs sooner than other treatment modalities. These results were not seen with Grade 3 sprains.15 If conservative measures do not provide ample healing, then surgery may be considered. Accordingly, the decision to perform surgery is not decided as a result of radiographic images but is based on a clinical decision and signs of examination under anesthesia.16

For ankle instability from tibia or fibula fractures, conservative management is used if the fracture is mild—e.g., hairline, closed and/or non-displaced fractures. Treatment can consist of tolerated weight bearing on the affected limb and/or casting. However, there is no consensus of treatment regarding mild fractures.17 For more complicated fractures such as an open fracture, physicians will gear towards surgical options. The surgical procedure chosen greatly depends on complications and morbidity. For example, it was found that sub-atmospheric pressure dressing prior to surgical correction and soft tissue reconstruction of an acute open tibia fracture was associated with reduced overall complications.18

When ankle instability is due to compromised integrity of the tendons, management is aimed at correcting the cause of the pathology. In cases where tendon laxity is a contributing factor, dextrose prolotherapy has shown to improve outcomes.19 For intrinsic tendinopathy, exercise therapy has been the mainstay of treatment.20 It has been shown that eccentric exercise is most effective in reducing pain as well as enabling proper function.21 With extrinsic causes, tendonitis may be reduced if the external factors are removed. For example, overuse injuries causing tendonitis can be avoided if the exercise regimen is decreased or proper stretching technique is used.20

Conclusion

When there is injury, conservative management is always preferred. For mild injuries, simply resting the affected limb can prove to be the best treatment. If further intervention is necessary, exercise or bandaging may be implemented and, if ligament laxity is a factor, prolotherapy may be useful. Surgical treatment will always be the last resort due to its invasive nature and complication risks.

Last updated on: April 28, 2016
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