What is it?
Sinus Tarsi Syndrome (STS) is pain and swelling in the sinus tarsi—a small, tunnel-like space located on the outer (lateral) side of the ankle. The sinus tarsi area is prone to inflammation and discomfort and often arises after an acute injury like an ankle sprain but can also be be caused by overuse, as well as different foot postures such as overpronation (when the foot rolls inward too much during walking or running).
Anatomy
The sinus tarsi sits below the bone on the outside of your ankle. It is a small canal located between two foot bones, the talus and the calcaneus (heel bone). This space acts as a passageway for nerves, blood vessels, and stabilising ligaments. Given its location on the outer side of the foot, the sinus tarsi is highly involved in ankle stability, balance, and foot mechanics. When inflammation develops in this area, the structures within the sinus tarsi can become irritated, leading to Sinus Tarsi Syndrome.
Signs and Symptoms
Common signs and symptoms include:
- Pain located below the bony area on the outer side of the ankle (lateral malleolus).
- Pain that worsens when walking, particularly on uneven or unstable surfaces.
- A feeling of instability or “wobbliness” in the ankle.
- Swelling or tenderness in the sinus tarsi region, which may feel like a small lump when palpated.
- Pain that may be worse during or after activity.
Symptoms may range from mild discomfort to significant pain that interferes with walking, balance, and daily activities.
Causes and Risk Factors
As previously mentioned, Sinus Tarsi Syndrome can occur after acute injury, overuse or due to risk factors such as foot posture. Common causes include:
- Ankle Sprains: One of the most frequent causes, especially when the ankle is sprained inward (inversion sprain). This type of injury stretches or damages the ligaments around the sinus tarsi, leading to inflammation.
- Overuse Injuries: People who increase their walking, running, or standing activity levels too quickly may experience STS due to repetitive strain on the ankle structures, especially if they are unaccustomed to these loads.
- Overpronation: This is when the foot rolls inward excessively while walking or running, causing misalignment and placing strain on the sinus tarsi. This can occur naturally in some people or may develop over time due to factors like poor footwear or weakened foot muscles.
- Previous Ankle Injuries: People who have a history of ankle sprains or other foot injuries are more susceptible to STS, as their ankles may be more prone to instability and overloading.
- Flat Feet: Individuals with flat feet are more likely to overpronate, increasing their risk of developing inflammation in the sinus tarsi area.
Diagnosis
Diagnosing Sinus Tarsi Syndrome involves a combination of a subjective assessment, physical examination, and sometimes imaging. Subjective assessment may include discussion about any recent or previous ankle injuries, current activity levels and symptoms.
Physical examination may include palpation to identify tenderness or swelling in the sinus tarsi area, range of motion tests to assess painful positions, as well as functional assessment like balance and strength testing. Other common causes of lateral ankle pain such as ligament or tendon injury will also be assessed.
Imaging
If the diagnosis is uncertain or symptoms are severe and not improving, imaging can help confirm Sinus Tarsi Syndrome:
- X-rays and CT scans may be used to rule out fractures or other bone-related issues but won’t show inflammation in the soft tissues.
- Ultrasound can show soft tissue injury or swelling, however shows no bone-related issues and sometimes is not accurate enough to identify STS.
- MRI scans are the gold standard imaging option, as they provide a clearer view of soft tissues, can reveal inflammation or fluid buildup in the sinus tarsi and will also assess bone-related issues.
Treatment
Treating Sinus Tarsi Syndrome typically involves reducing inflammation, managing pain, and improving ankle stability. Treatment options can range from conservative measures, such as physiotherapy, to medical interventions for more persistent cases.
Physiotherapy and Rehabilitation
Physiotherapy is a core treatment for STS, as it helps address the root causes and strengthens the supporting muscles of the foot and ankle. A physiotherapist may provide the following:
- Rest and Activity Modification: Reducing or temporarily stopping activities that aggravate the condition, like high-impact exercises, is often essential in the initial stages of recovery.
- Manual Therapy: Physiotherapists may use hands-on techniques to relieve tightness, improve joint mobility, and reduce pain in the affected area.
- Stretching and Strengthening Exercises: Targeted exercises can strengthen the muscles around the ankle, improving stability and reducing stress on the sinus tarsi. Specific stretches for the calves, Achilles tendon, and foot muscles may help relieve tension that contributes to overpronation.
- Balance and Proprioception Training: This involves exercises to improve balance and ankle control, which can help prevent reinjury and reduce feelings of instability.
- Taping and Orthotic Support: Taping techniques can provide immediate support and reduce strain on the sinus tarsi. Custom orthotics or arch supports can correct foot posture and reduce overpronation, preventing unnecessary strain on the ankle.
Medical and Other Conservative Treatments
In addition to physiotherapy, some individuals may benefit from other conservative treatments. These can include:
- Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): These can help reduce pain and inflammation, especially in the initial stages.
- Steroid Injections: In cases where pain and swelling persist, a doctor may recommend a corticosteroid injection directly into the sinus tarsi area. This can provide relief but is generally considered only after other treatments have been tried.
- Footwear Modification: Proper footwear with adequate arch support and cushioning can help improve foot alignment and reduce the risk of exacerbating the condition. A podiatrist can assist in assessing your footwear and making recommendations.
- Ultrasound Therapy: Therapeutic ultrasound may sometimes be used to reduce pain and improve circulation to the area.
Prognosis
The outlook for Sinus Tarsi Syndrome is generally positive with appropriate treatment and management. In many cases, symptoms improve significantly within several weeks of treatment. However, the duration of recovery depends on factors such as the severity of the condition, adherence to treatment, and the presence of underlying issues like overpronation or flat feet.
People who have mild cases or seek early treatment tend to recover faster and can often return to normal activities without long-term issues. For those with more persistent symptoms, gradual progress through physiotherapy, footwear adjustments, and other conservative measures usually leads to improvement. Severe or long-standing cases may take several months to resolve fully, but the majority of individuals experience a reduction in symptoms and are able to resume most of their usual activities.
This information is provided for educational purposes only. Always consult your physiotherapist or other health professional.