Sinus Tarsi Syndrome
Sinus Tarsi Syndrome (STS) is a condition that affects the outside of the foot and ankle.
The sinus tarsi is a tube or tunnel that forms between the talus and the calcaneus bones. Sinus tarsi syndrome is pain or injury to this area. It is most commonly caused by traumatic injury to the ankle/foot (ankle sprain) or through overuse (such as repetitive standing or walking).
It may also occur in a person who has a pes planus or an over-pronated foot (flat foot) posture, which can cause excessive compression in the sinus tarsi.
The sinus tarsi is found in between the talus and the calcaneus bones and contains structures that are responsible for stability and proprioception.
The joint between the talus and calcaneus is known as the subtalar joint. This articulation includes 3 facets: an anterior, middle and posterior facet. Variation in structure of those facets affects the stability of the subtalar joint.
This subtalar joint is reinforced by the superficial extrinsic ligaments (calcaneofibular and deltoid ligament) and the deeper intrinsic ligaments (the interosseus, the talo-calcaneal ligament (number 5 in figure 1), the cervical ligament (number 6 in figure 1)) and the medial, lateral and intermediate roots of the inferior extensor retinaculum which all provide extra stability to the joint.
Ruptures or damage to the intrinsic ligaments results in increased movement at the subtalar joint, causing instability. It has also been suggested that the sinus tarsi is responsible for nociception and proprioception (our brains awareness of where the body is in space). Hence injury to this area can affect our balance and predispose us to future ankle injuries.
Most commonly people who present with this STS have had a previous traumatic lateral ankle sprain or multiple sprains which results in injuries to the interosseous and cervical ligaments.
Inflammation and haemorrhage as a result of the injury lead to synovitis and infiltration of fibrotic tissue into the sinus tarsi space leading to pain and swelling.
Sinus tarsi syndrome can also occur as a result of repetitive compression through the area, for example to people who have flat or pronated feet, where the lateral aspect of the ankle and sinus tarsi are repetitively pinched. In this situation the talus and calcaneus are pressed together as a result of the deformation causing bone to bone contact which can create inflammation or arthritis in the sinus tarsi.
Symptoms of STS include:
Pain: tends to be localized to the sinus tarsi area and feels deep inside the ankle.
Pain that gets worse with prolonged activities such as walking or running and eases with rest.
Instability: especially when exercising on uneven ground or slopes, when jumping or quickly changing direction.
Stiffness: the ankle may feel stiff first thing in the morning and then improve as you move around and loosen up.
Tenderness to touch: around the outside and front of the ankle.
Pain with Ankle Movements: especially inversion (turning the sole of the foot inwards) and plantarflexion (pointing the foot down).
Symptoms of sinus tarsi syndrome tend to come on gradually over time. If you have injured the ankle, the symptoms of the initial injury tend to never fully settle, so even though the injured ligament heals properly, you are left with pain due to the resultant irritation of the sinus tarsi area.
When diagnosed early, STS responds very well to conservative care and can improve quickly. However, if the problem isn’t identified early and rehab not adhered to correctly it can prolong the healing process and in some cases progress to a chronic irritation.
Conservative treatment, initially, involves resting from the aggravating activities which, if not avoided, will continue to irritate the tissues that are already hypersensitive. In this early period ice and anti-inflammatories are useful to reduce swelling and control pain. Your therapist will apply soft tissue release to the lower leg, foot and ankle as well as mobilisations to the subtalar and talocrural joints. Ultrasound therapy can assist in reducing swelling and taping is usually incorporated to unload the aggravated structures and provide better support to the foot.
The underlying cause of STS is often poor foot posture. If this is identified to be the case your therapist will also give your foot extra stability by taping, looking at alternative footwear or introducing an orthotic into your shoe. This provides better longer-term improvement by enhancing the posture of the foot and reducing strain on the sinus tarsi.
Once pain and inflammation have begun to subside a stretching and exercise program will be provided to start strengthening the muscles around the ankle.
At the same time, it is critical to include a proprioception retraining program, especially for those people whose STS has arisen secondary to chronic ankle instability. This program aims to stabilise the ankle further and minimise the risk of future sprains.
Whilst rarely needed, surgery is another option if conservative treatment has failed. This will usually involve removal of any chronic synovitis (inflammation) and scar tissue, reconstruction of the ligaments or arthrodesis (fusion of the subtalar joint).
3 tips to reduce your chances of developing STS include:
1. Wear correct footwear – this applies to several foot and ankle related conditions and is so important as it is our first base of stability connecting us to the floor.
2. If you have sprained your ankle, ensure you follow through with a complete rehabilitation program. The number one cause of ankle sprains is previous ankle sprains that have not repaired correctly.
3. Maintain good strength and stability in the muscles that surround the ankle by engaging in regular exercise.
So that’s an overview of how sinus tarsi syndrome occurs. If you have any questions or comments please e-mail us at firstname.lastname@example.org and we will be happy to answer them for you.
If you suffer with persistent pain through the side of the ankle, feel free to call us on (08) 9486 8653 and our therapists will be happy to chat with you about the best management plan.