Detecting The Cause Of Chronic Ankle Pain
It is often challenging to treat patients who have chronic ankle pain. There is an array of potential causes so it’s essential to be very thorough in arriving at your diagnosis. For example, consider the case of an active 34-year-old male who runs and plays tennis, basketball and beach volleyball. In the past six months, he says he has had acute ankle pain in certain situations and chronic pain in other situations.
More specifically, the patient says the pain is worst when he is engaged in activities involving toe raises or when he is on the ball of his foot for extended periods of time. He also says there has been an increase in chronic pain with normal ambulation in the previous three months. According to the patient, the pain is accentuated when he wears certain shoes or if he is barefoot for long periods of time. He has had a history of multiple ankle sprains in the past 20 years, with the last one occurring only a year ago. He has not had one recently only because he has had to decrease his level of activity due to the increased pain.
Yet the region of pain has changed in the previous two months. Prior to that period, he was able to perform sports activities, yet he would experience soreness in the anterior ankle region the next day. In the past two months, he has experienced that same soreness with increased activity, yet he also has a chronic nagging pain in the posterior and retro-fibular regions of the painful ankle. The patient feels a “bruising” of the posterior ankle with a dull ache after a short period of ambulation.
What The Examination Reveals
A physical examination reveals a fit young man in no acute distress. The patient stands with a fairly rectus stance. There is a slight cavus to the foot, yet it is stable in all planes. A mild genu recurvatum is noted during lateral observation. Upon performing a pedal exam, it is noted that the patient has bilateral symmetrical pulses. Neurologically, all examinations are normal without loss of any sensatory or deep tendon reflexes. Dermatologically, there is mild edema on the antero-lateral ankle with extension on the posterior region of the fibular malleolus. There is no ecchymosis or erythema.
The patient has a full range of motion without guarding or pain on the lateral ankle region. There is tenderness in the posterior fibula along the course of both peroneal tendons. It is noted that the peroneal tendons are painful below the fibular malleolus and the patient has decreased pain along the more distal regions of the two tendons. There is a positive anterior drawer of the ankle with a lateral ankle “pucker” sign. There is minimal lateral varus instability or subtalar instability. The Achilles is slightly tight when the patient’s knee is straight, yet it’s normal with the knee bent 90 degrees.
What Is The Differential Diagnosis?
1. An osteochondral lesion of the medial or lateral ankle
2. Sinus tarsi syndrome
3. Lateral ankle instability with a tear of one or more lateral ankle ligaments
4. A tear of one or both of the peroneal tendons
Pertinent Points On Testing
Depending on your level of suspicion, you would want to order tests that would cover the majority, if not all, of the above possibilities. Begin with standard radiographs. Although there is a great deal of information on the radiographs, you’ll need a MRI or diagnostic ultrasound to detect soft tissue disorders. In most cases, I believe the MRI is a better test unless you have a great deal of expertise in ultrasound.
In this case, standard radiographs show a well-positioned ankle without signs of degenerative changes. The images show no osteochondral lesion and a stable ankle mortise. On the anterior views, there is a large bone fragment in the anterior lateral gutter of the ankle, which is in close proximity to the distal fibula. The lateral radiograph reveals a well positioned rearfoot and ankle with mild anterior displacement of the talus in the ankle mortise.
The MRI reveals a chronic tear with thickening of the anterior-talofibular ligament. There is marrow edema of the distal fibula without sign of fracture. The MRI confirms the radiographic findings of the bone fragment in the lateral gutter and the absence of osteochondral lesions. Tendon examination reveals normal tendon anatomy except for thickening and increased intra-substance signal within the peroneus brevis tendon. This increase in signal is present 3 cm proximal to the fibular malleolus and extends distally 1 cm past the anterior tip of the fibular malleolus.
1. You can rule out an osteochondral lesion due to a negative radiograph and MRI. Furthermore, with osteochondral lesion pain, the patient will have deep joint pain with a feeling of locking of the joint from time to time. Although this is still a possibility, it is highly unlikely. If you’re still suspicious, order a CT scan.
2. Sinus tarsi syndrome secondary to a tear of the interosseous ligament or inflammation is possible but not very likely. You must take care to avoid confusing sinus tarsi pain with peroneal tendonitis or tear as the two locations are in close proximity and difficult to diagnose. The MRI did not show any inflammation of the sinus tarsi or ligament tear in that region.If you are not convinced, try a diagnostic block of the sinus tarsi and make sure that the block is deep so as not to involve the peroneal tendon region.
3. It is obvious a great deal of the symptoms in this patient are secondary to a chronic anterior ankle instability. You can see the tear on the MRI and the patient notes instability with toe motions. Furthermore, there is a large bone fragment in the lateral fibular gutter, which is usually secondary to an avulsion fracture of the tip of the fibular at the attachment points of one or more lateral ankle ligaments.
4. The ultimate question in this case is why does the patient have involvement of the peroneal tendons and why has it only flared up in the past two months? Furthermore, is this a problem that requires treatment or is it a secondary symptomatic problem? Usually, peroneal pain is secondary to an acute tear or an overuse injury of the tendon.
In this case, it is due to an overuse injury, secondary to the ankle instability. In cases of chronic ankle instability, it is not uncommon to have pain in the region of the peroneal tendons as they attempt to stabilize the lateral ankle region. It is rare to have a combination of peroneal tendon tear and ankle instability secondary to a ligament tear both on an acute basis. In most cases, there is a chronic instability which leads to peroneal tendonitis and possible partial intrasubstance tears. However, in most cases, the increased intrasubstance signal we see on the MRI is secondary to a tendonitis and not a tear of the tendon.
Diagnosis And Treatment
The best way to differentiate peroneal tendonitis from a partial tear is to immobilize the ankle for a short period of time. If the tendonitis resolves and the pain in the posterior ankle decreases, you’re likely dealing with a secondary problem. If the pain persists in the posterior peroneal region, there is a likely a partial tear.
I place the patient in a BK walker for two weeks, following with one week of a lace-up ankle brace. If the pain resolves with the ankle brace, the intrasubstance signal is a tendonitis. If you are still on the fence, you should check the peroneal tendons for tears at the same time you repair the anterior ankle ligament and remove the loose bone in the lateral gutter.
Where you make the incision will depend on whether you are performing any peroneal work. If you intend to check the peroneal tendons, make a lateral incision on the surface of the fibula. Undermine the skin to reach the anterior ankle and the peroneal tendons. If you are not performing peroneal work, make an anterior ankle incision on the anterior aspect of the fibula, curving the incision posteriorly on the distal aspect of the fibula.
I prefer doing the modified Brostrom primary ligament repair in most ankle stabilizations. If you find severe degeneration of the lateral ligaments on MRI or the patient is very lax, you may wish to add a Watson modification by routing part of the peroneus brevis tendon through the fibula in addition to the Brostrom procedure in order to increase anterior drawer stability. Furthermore, do not forget to check varus stability after removing the loose bone since you may detach the calcaneo-fibular ligament with removal of the bone fragment. If you do remove the calcaneo-fibular ligament, reattach it to the fibula as part of the modified Brostrom procedure.
Dr. Baravarian is an Assistant Clinical Professor in the Department of Surgery/Division of Podiatric Surgery of the UCLA School of Medicine. His e-mail address is Bbaravarian@mednet.ucla.edu.