Lateral Ankle Sprain and Chronic Ankle Instability

By
Robert Rinaldi, DPM
Posted July 1st, 2009

The commonly occurring lateral ankle sprain, also called an inversion sprain, can be the precursor to painful and disabling chronic ankle instability. The ankle twist, rollover, or sprain may be the most overlooked athletic injury, and for that reason may also be amongst the worst. A common ankle sprain can lead to ankle instability, cartilage damage, arthritis, and a lifetime of ankle pain. It often occurs in sports that involve jumping, moving side to side, rapid direction changes, and for runners and hikers, running and hiking on uneven surfaces. Once an ankle sprain occurs, ligaments that are responsible for ankle function may heal, but never return to normal strength and full function.
ANKLE ANATOMY
The anterior talo-fibular ligament, commonly referred to as the ATFL, resides on the lateral side of the foot. One end attaches to the talus in the foot, and the other end to the fibula in the lower leg. The ATFL works in conjunction with the calcaneal-fibular ligament and the posterior talo-fibular ligament, but in a lateral ankle sprain it is the ATFL that is usually injured.
The lateral ankle sprain can be an uncomplicated injury or it can be very complicated, involving bone fracture and displacement. The complicated injuries usually get the appropriate treatment attention. It’s the uncomplicated sprains that too often fall into a treatment program that involves only rest for a few days, leaving the ATFL susceptible to re-injury.
Too many times the lateral ankle sprain is referred to as a “simple sprain.” I do not believe a “simple sprain” exists. Ligaments want to heal, but in the ankle, because of the normal stresses of ambulation, the ligaments will heal, but a laxity will remain. This laxity will put the ankle at risk for additional sprain and twist injuries.
Tendons are also at risk in an ankle sprain. Both the peroneal longus and peroneal brevis tendons are susceptible to injury during an ankle sprain. This muscle-tendon complex is important to normal foot and ankle function, and in the prevention of the inversion sprain. Malfunction of this musculo-tendon unit, combined with injury to the ATFL, will increase the risk for recurring ankle sprains and eventual instability.
MECHANORECEPTORS
The lateral side of the ankle is endowed with nerve endings that communicate with the brain, creating a constant awareness of ankle joint position at any given time in the gait cycle. Recent biomechanical and neurological studies lead to conclusions that these neuromuscular pathways are responsible, in part, for ankle stabilization. These same receptors can be interrupted when an inversion sprain occurs. Functional disruption of the ATFL and treatment that is less than optimal will lead to recurring ankle injury, loss of ligament structural support, and damage to the co-existing mechanoreceptors, all of which ultimately contributes to further and chronic instability.
CHRONIC ANKLE INSTABILITY
Acute lateral ankle sprains are successfully treated most of the time, however, studies indicate that 10 to 20 percent of all acute injury goes on to become a chronic recurring problem. The key indicator that ankle instability exists is not pain, but a multitude of recurring twists and rollovers of the ankle joint. These do not always cause disability, pain, swelling, or even the telltale black-and-blue discoloration associated with an ankle sprain. The ankle joint will get to a point that it can easily move out of control and position. With each additional incident, instability of the ankle will increase and less provocation is needed for the rollover to happen. An athlete who is aware of frequent rollovers will become hesitant and insecure about the biomechanical movements necessary to pursue his or her sport.
DIAGNOSIS AND TREATMENT REGIMES
Any lateral ankle sprain should be considered to include injury to the ATFL, as well as the peroneal longus and peroneal brevis tendons, until proven otherwise. Examination by X-ray is primary, and must include stressed ankle views to evaluate the position of the talus in the ankle mortise. An increased talar tilt within the mortise on an anterior/posterior x-ray indicates the possibility of an ATFL injury.
The ATFL is very deep in the ankle, running bone-to-bone, from the talus to the fibula. Recent studies have concluded that when it’s torn or ruptured, the peroneal tendons are most likely injured as well. These tendons course through a gossamer structure called the retinaculum. This musculo-tendon structure aids in stabilizing the foot and ankle, helping to prevent recurring inversion sprains.
Once an inversion sprain is diagnosed, it must be taken seriously. This is accomplished with the use of cam-walkers followed by air splints to immobilize the ankle. The ATFL, like any ligamentous structure, wants to heal and heal strong. The retinaculum, though thin and subtle, is also a ligament, and it wants to follow suit. If we provide stability to the damaged ankle by using a cam-walker and air splint, healing will occur in about three weeks. At this point, return to sport is possible without hesitation.
An ankle injury that is not rigorously treated may progress to recurring inversion sprains. When this occurs, MRI imaging will identify the injured structures and surgery should be considered to restore stability of the ankle joint. Platelet Rich Plasma therapy has proven to be a successful non-invasive treatment in many instances, and should not be overlooked.
Robert Rinaldi is a board-certified podiatrist and podiatric surgeon at the Gifford Medical Center in Randolph, VT. He is a fellow and a founding member of the American Academy of Podiatric Sports Medicine, and a podiatric consultant to the Dartmouth College track and cross-country teams. He is a former nationally ranked long-distance runner, having competed in 25 world-class marathons. You can reach him at Gifford Sports Medicine and Surgery Clinics in Randolph, VT, or at the Sharon Health Clinic in Sharon, VT, 802-728-2490 or 802-763-8000 or at rrinaldi@giffordmed.org.