The sinus tarsi, known as the “eye of the foot”. It is a small cavity located on the outside of the ankle between the talus and calcaneus bones. This can be felt as a deeper spot on the outside of the ankle that you can push your finger into.
This cavity contains numerous anatomical structures. These include ligaments, joint capsule, blood vessels, fatty tissue and nerve endings that play a vital role to the balance receptors in the ankle.
These structures within the sinus tarsi may be injured following an ankle sprain. Poor foot biomechanics and/or structural foot abnormalities could also make a person susceptible to this condition.
Outside ankle sprains attribute to 70-80% of cases. The remaining 20-30% is due to “pinching” or impingement of the soft tissues in the sinus tarsi due to very flat feet.
In Sinus Tarsi Syndrome, the structures in the canal show signs of inflammation, cellular damage, scar tissue and possible cysts.
Treatment for Sinus Tarsi Syndrome should be immediate. When the injury becomes chronic the rate of healing slows significantly. This results in longer recovery times and increased chance of future reoccurrence.
Causes of Sinus Tarsi Syndrome (Outside Ankle Pain):
- Inversion ankle sprain (rolling out).
- Repetitive strain associated with walking or running.
- Excessively pronated flat foot (rolling in).
Contributing Factors of Sinus Tarsi Syndrome (Outside Ankle Pain):
- Poor flexibility and/ or muscle weakness.
- History of ankle sprains and poor balance receptors and weakness in the ankle joint.
- Inappropriate training and/or inappropriate footwear.
- Poor foot biomechanics or structural abnormalities.
Signs and Symptoms of Sinus Tarsi Syndrome (Outside Ankle Pain):
- Pain +/- swelling over the outside of the ankle, which may be difficult to pin point.
- Feeling of instability, especially when walking on slopes or uneven surfaces.
- A sharp sensation of pinching pain, when the foot is lifted up, for instance when walking-up stairs.
- Symptoms are typically worse in the morning and can slowly improves as the foot warms up.
- Reduction on muscle bulk on the outside of the leg during walking.
- MRI is the investigation of choice as this cavity is hard to investigate with X-ray and ultrasound alone. Fluid within the cavity, inflammation and fibrosis are definitive of this syndrome.
- The pain will be temporarily relieved by injecting local anaesthetic into the canal. This is used as a diagnostic test only not a treatment.
Treatment for Sinus Tarsi Syndrome (Outside Ankle Pain):
- R.I.C.E regime (rest, ice, compress, elevate) for acute injuries within the first 48 hours.
- Anti-inflammatory medication may be beneficial in the initial phase of this injury.
- Sufficient rest from any activity that increases pain levels.
- Prolotherapy into the joint has been found to be very beneficial along with Foot Mobilisation Therapy and dry needling.
- Mechanical support to the foot, such as a customised foot orthoses to correct the poor function of the foot and tendons around the ankle, resulting in excessive movement.
- Functional rehabilitation of Achilles tendon, peroneal muscles and proprioception trainings, with a gradual return to activity, under the direct guidance of a podiatrist.
- Appropraite supportive footwear.
- Moon boot in very severe cases to allow healing without further tissue damage.
Note: Conservative treatment is very effective and surgery is not necessary unless conservative treatment fails .
Two Surgical Techniques for Sinus Tarsi Syndrome:
- Open surgery with excision of the entire contents of the sinus tarsi.
- Closed surgery with key hole examination and cleaning up of the posterior subtalar joint and sinus tarsi.
Well Heeled Podiatry can quickly assess, diagnose and treat Sinus Tarsi Syndrome, giving you pain relief to allow you to get on with the things you love doing.