The Sinus Tarsi Syndrome
A Cause of Chronic Ankle Pain
Victor B. Klausner, DO; Mark E. McKeigue, DO
THE PHYSICIAN AND SPORTSMEDICINE - VOL 28 - NO. 5 - MAY 2000
In Brief: Correctly diagnosing sinus tarsi syndrome is important because it is frequently misdiagnosed as chronic ankle sprain and, if improperly treated, will result in chronic pain and disability. A detailed history and physical examination will usually confirm the diagnosis. Clues include pain and instability when walking on uneven surfaces, and resolution of pain when the affected foot is at rest. Conservative treatment of sinus tarsi syndrome is usually considered first and consists of consecutive corticosteroid injections into the tarsal canal, along with physical therapy and correction of foot biomechanics. Sinus tarsectomy is reserved for patients who do not respond to conservative treatment.
Sinus tarsi syndrome is a frequently misdiagnosed condition in which patients have pain over the lateral aspect of the ankle (the sinus tarsi region) and the sensation of hindfoot instability. Patients often have a history of an inversion ankle injury that results in chronic pain (1). (See "Case Study: Unresolved Ankle Pain and Instability," page 79.) The syndrome was first described by O'Connor (2) in 1958, and since then the understanding of syndrome pathophysiology has advanced greatly. With a better understanding of this diagnosis, a specific treatment plan can be initiated with excellent results.
Anatomy and Mechanism
The sinus tarsi, also known as the talocalcaneal sulcus, is an anatomic space between the inferior neck of the talus and the superior aspect of the distal calcaneus (figure 1). The space continues with the tarsal canal, a funnel-shaped space that extends medially to a small opening posterior to the sustentaculum tali. Fat and ligaments occupy the space and are supplied by the tarsal canal artery, a branch of the posterior tibial artery.
Ligamentous structures within the tarsal canal include the inferior attachment of the extensor retinaculum of the foot, the interosseous talocalcaneal ligament, and the cervical ligament. The main ligament is the interosseous talocalcaneal, a wide and very strong ligament that originates from a broad attachment in the middle of the canal on the surface of the calcaneus and runs anteromedially to the deepest portion of the tarsal canal, where it inserts on the talus. The cervical ligament is a smaller band that has its origin on the lateral calcaneus just medial to the attachment of the extensor retinaculum of the foot and passes medially through the center of the canal as it inserts on the talus (3).
The most common cause of sinus tarsi syndrome is a severe inversion ankle injury. A simple ankle sprain—a mild inversion injury—differs from sinus tarsi syndrome by the force required to produce the injury. In a simple ankle sprain, damage occurs to the stabilizing ligaments of the lateral ankle, while in sinus tarsi syndrome the force is enough to tear the tarsal canal ligaments. (See "Persistent Pain After Ankle Sprain: Targeting the Cause," December 1997, page 58.) Common activities for inversion injuries include jumping sports and activities such as inadvertently stepping in a hole or off a curb. Other less common causes of sinus tarsi syndrome include hindfoot deformities and inflammatory conditions such as rheumatoid arthritis and gout.
Tarsal canal ligaments maintain alignment between the talus and calcaneus and limit inversion. The main stabilizing ligament of the lateral ankle is the calcaneofibular ligament (4). In addition, the interosseous talocalcaneal ligament is taut when the foot is supinated, and the cervical ligament helps resist hindfoot varus forces. With inversion trauma, the ligaments are usually injured in the following order: anterior talofibular ligament, calcaneofibular ligament, cervical ligament, and interosseous talocalcaneal ligament. The more severe the injury incurred, the more of these ligaments are injured. Thus, tarsal canal ligament injury never occurs as an isolated lesion but will always involve rupture of the calcaneofibular ligament or the anterior talofibular ligament (5).
History and Physical Exam
Patients who have sinus tarsi syndrome typically present immediately after the injury with diffuse swelling and pain over the lateral ankle. They have difficulty bearing weight on the affected foot and usually require crutches. At this point the injury is indistinguishable from an acute ankle sprain and should be treated as such.
As the swelling decreases over several weeks, patients exhibit less pain with ambulation but will continue to have pain and a feeling of hindfoot instability when they walk down steps or on uneven surfaces. Pain frequently disappears when the foot is at rest or when immobilized with a brace. This information provides critical clues to the diagnosis of sinus tarsi syndrome (table 1).
TABLE 1. Characteristic Clinical Signs of Sinus Tarsi Syndrome
Pain that is:
Increased by firm palpation of the lateral opening of the sinus tarsi;
Severe when patient is standing, walking on uneven surfaces, or during supination and adduction of the foot; and
Eased with firm bandage or support that holds the heel in pronation or valgus postion
Feeling of hindfoot instability when walking on uneven surfaces
Local anesthetic injection into the sinus tarsi reduces sensation of instability for a few hours
Routine clinical and radiologic stress exams do not reveal signs of instability of ankle joint; standard anterior posterior and lateral radiographs are normal
Adapted from Taillard W, Meyer JM, Garcia J, et al: The sinus tarsi syndrome. Int Orthop 1981;5(2):117-130.
Understanding the diagnosis and treatment plan of sinus tarsi syndrome is important because the condition is frequently misdiagnosed as chronic ankle sprain. The mistaken diagnosis is understandable because both conditions share the same mechanism of injury and involve sprains to the lateral ligaments of the ankle. Subtalar ligament injuries, however, lead to chronic inflammation in the sinus tarsi canal and minor hindfoot instability.
Physical examination. The physical examination will reveal exquisite tenderness over the sinus tarsi. The proximity of the anterior talofibular ligament to the sinus tarsi requires very specific palpation to identify the source of pain. One simple technique to detect tenderness is to use the eraser on a pencil to press on these structures one at a time (figure 2).
Pain can also be reproduced by testing foot motion in extreme supination and adduction. Pain and instability can be reproduced by having the patient walk down steps or on an uneven surface. The diagnosis of sinus tarsi syndrome is likely if symptoms are relieved by an injection of 2 to 3 mL of local anesthetic into the tarsal canal (figure 3) (1).
It is very important to evaluate for ankle instability, because demonstrated ankle instability will rule out sinus tarsi syndrome. Ankle instability is diagnosed by excessive talar motion on inversion or on anterior drawer stress tests when compared with the opposite side. Unilateral instability is always pathologic.
Because sinus tarsi syndrome involves subtalar ligament sprains and a subjective sense of instability, one might expect to discern increased subtalar motion with a physical exam. This is not the case. Studies performed on amputation specimens in which the cervical and interosseous talocalcaneal ligaments were severed showed a negligible increase in total range of subtalar joint movement (no greater than 2.6° in any plane). Although this movement represents a 43% increase in motion, it is hardly detectable, and testing subtalar motion will rarely be informative (6).
Examination of foot biomechanics will often reveal a hindfoot varus deformity that contributes to chronic inversion stress on the subtalar joint. (Hindfoot varus is an inversion of the calcaneus with the subtalar joint in a neutral position.) A common physical compensatory mechanism resulting from subtalar pain and instability is peroneal spasm with associated pes planus and weak eversion (7).
Although the diagnosis of sinus tarsi syndrome is usually made clinically, plain or stress radiographs can help rule out associated pathology (eg, arthritis, fracture, and instability). Patients with sinus tarsi syndrome typically have normal radiographs. Magnetic resonance imaging (MRI) is by far the most useful tool in assessing the tarsal canal. Pathologic changes that occur with sinus tarsi syndrome are easily visualized, and inflammatory and fibrotic tissue infiltration can be seen by comparing T1- and T2-weighted images. Subtalar ligaments can also be evaluated for injury, but they are sometimes not visualized because of inflammatory infiltration or simply because they have been disrupted. Calcaneofibular ligament injury, meniscoid lesions, and talar osteochondral injury can also be detected with MRI, but the technique should be reserved only for cases in which the diagnosis is unclear or if surgery is being considered.
Before the advent of MRI, diagnosis was often done with arthrography, but the technique is rarely used now because of its invasive nature. Electromyography is not helpful for diagnosis, but it can confirm peroneal muscle attenuation (3).
Conservative therapy. Initial treatment is conservative. In many cases, symptoms can be completely relieved by repeated injections of local anesthetic and corticosteroid into the sinus tarsi. Komprda (8) noted that 63% of 116 patients had improvement after a series of injections given at weekly intervals (one injection per session for 3 to 6 weeks). Kuwada (9) studied 88 patients, 24% of whom had long-term relief after physical therapy and one injection a week for 2 weeks.
Care must be taken, because repeated injections of corticosteroid are associated with several risks. Local side effects include infection, subcutaneous atrophy, and skin depigmentation. Systemic side effects of oral corticosteroids include menstrual irregularity, osteoporosis, adrenal suppression, impaired glucose tolerance, and steroid arthropathy. Using proper technique and not exceeding the recommended maximum steroid dosage can minimize side effects.
Treatment should also focus on correction of dysfunctional feet with orthoses and physical therapy. Physical therapy should address retraining of the peroneal and calf muscles and include a general strengthening and proprioception program with an exercise band and a tilt board (1). Additional measures include those for ankle sprains (rest, immobilization, cold, etc).
Surgery. If conservative treatment fails, a sinus tarsectomy should be considered. Tarsectomy involves excision of the tarsal canal contents, including the fat plug, nerves, damaged capsule, and, occasionally, damaged ligaments. If the anterior talofibular ligament is ruptured, ligamentoplasty is also done using a portion of the peroneus brevis. After surgery, patients can walk as much as tolerated in a special shoe for 1 to 2 weeks. Normally, they are able to resume full activity in 4 to 6 weeks.
Sinus tarsectomy has an excellent cure rate. All of the 66 patients who underwent sinus tarsectomy in Kuwada's study (9) had long-term relief. Similarly, Taillard et al (10) noted a cure rate of 90% in 15 patients requiring surgery. For recalcitrant cases, triple arthrodesis of the ankle (fusion of the subtalar, calcaneocuboid, and talonavicular joints) may be the only surgical solution (9); however, it is surgery of last resort.
With a thorough working knowledge of the diagnosis of sinus tarsi syndrome, the physician can effectively treat this condition. The challenge facing the clinician is distinguishing sinus tarsi syndrome from the other causes of chronic ankle pain and guiding the patient's recovery once the diagnosis is certain.
Case Study: Unresolved Ankle Pain and Instability
A 51-year-old man was referred to our clinic 5 months after an inversion ankle injury.
History. The patient stated that he twisted his ankle while running and stepping off a curb. He said that he felt severe pain and had swelling in his lateral ankle immediately after the injury. X-rays of the ankle taken in the emergency department revealed no fractures or degenerative changes. The patient was treated for a lateral ankle sprain with a rigid ankle brace, crutches, nonsteroidal anti-inflammatory drugs, range-of-motion exercises, and ice.
After 1 month, the swelling resolved, and the pain was about half as severe. The patient began a home strengthening program, and over the next month the pain diminished 70% from that at initial injury. The patient was referred for formal physical therapy for aggressive strengthening and proprioception exercises and was also given nonprescription arch supports. At that time, he reported intermittent ankle pain and a feeling of instability when descending stairs or when walking on uneven surfaces. Although the physical therapy allowed the patient to regain full ankle range of motion and improved strength and proprioception, ankle pain and instability persisted.
Physical examination. Left ankle range of motion was equal to that of the right (0° dorsiflexion, 40° plantar flexion, 35° inversion, 20° eversion). Manual muscle tests revealed mild weakness of inversion and eversion; no effusion was noted. Palpation showed mild tenderness over the tibiofibular ligament and extreme tenderness over the lateral subtalar joint and sinus tarsi. The anterior drawer, talar tilt, and squeeze tests were all negative. Foot biomechanics revealed mild pes planus with hindfoot varus and external tibial rotation. Functional testing revealed a normal gait on a level surface and an antalgic gait while descending stairs.
Imaging and differential diagnosis. X-rays of the left foot revealed a small calcification in the area of the calcaneofibular ligament. No fractures or degenerative changes were noted. The differential diagnosis included chronic ankle sprain, sinus tarsi syndrome, osteochondral injury of the talus, inflammatory arthropathy, and subtalar meniscoid lesion.
Treatment. The patient's sinus tarsi was injected with 3 mL of 1% lidocaine hydrochloride and 1 mL of betamethasone sodium phosphate combined with betamethasone acetate. Ankle pain and instability while descending stairs resolved immediately after the injection. A working diagnosis of sinus tarsi syndrome was made, and two more injections were performed at weekly intervals, one injection per week. The patient improved 50% after the injections and was sent to physical therapy sessions to improve strength and proprioception of the tibialis posterior and peroneal muscles. Custom orthoses were prescribed to compensate for the patient's mild pes planus with hindfoot varus. At 3-month and 1-year follow-up visits the patient had no residual symptoms of pain or instability.
Dr Klausner clinical instructor of family medicine at Midwestern University, Chicago College of Osteopathic Medicine, Downers Grove, Illinois, and Dr Mckeigue is a clinical professor of family practice and director of the sports medicine fellowship at Midwestern University in Downers Grove, Illinois. Address correspondence to Victor B Klausner, DO, St James Hospital and Osteopathic Medical Center, 20201 South Crawford Ave, Olympia Fields, IL 60461.