The owner of the clinic where I practice physical therapy is known as a foot and ankle expert. She is also a former ballet dancer. This means that we see quite a few ballet dancers. I have learned many things from treating this population. For one, I know more ballet terms than the average person. For two, I know more about common and not-so-common injuries in ballet. One of the conditions that I have learned about is os trigonum syndrome. This condition occurs more in ballet because it requires so much forceful plantarflexion (pointing down) of the foot. It is treatable, and ballet dancers are not the only susceptible to it. Read on to learn more about os trigonum syndrome. Let’s start with anatomy!
Joints of the ankle
The ankle has two main joints. These are the talocrural and subtalar joints.
- The talocrural joint is made up of the talus and the lower ends of the tibia, and fibula. The talus is a bone that sits above the calcaneus (the heel bone). The tibia and fibula are the lower leg bones. This joint allows for plantar flexion (pointing the foot down) and dorsiflexion (pointing the foot up).
- The subtalar joint is made up of the talus and the calcaneus. This joint allows for eversion and inversion. Eversion is when the ankle and arch roll inward and inversion is when the ankle and arch roll outward
- All four motions of the ankle are vital in order for the foot and ankle to walk and move normally.
What is the os trigonum?
The os trigonum is an extra bone at the back of the talus. It often fuses with the talus but in up to 15% of people, it remains a separate bone. It can be on one or both feet. It is small, usually less on 1cm in size. It sits right beside the tendon of the flexor hallucis longus. The flexor hallucis longus is a muscle that is located in the back of the leg. It flexes or bends the big toe. This tendon can also become inflamed and cause pain with os trigonum syndrome.
What is os trigonum syndrome?
Os trigonum syndrome is a condition that causes pain in the back of the ankle when plantarflexing (pointing) the foot. It is caused when the os trigonum is pinched between the calcaneus, talus, and tibia. Os trigonum syndrome is also known as a type of posterior ankle impingement.
Typically the presence of an os trigonum does not cause problems or pain in the ankle. Most people do not even know it is there. There are two different ways to cause os trigonum syndrome.
- Overuse – There are certain activities that can cause the os trigonum to become pinched and inflamed. These include activities that require repeated or sustained plantarflexion.
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- Ballet – especially en pointe or Demi-pointe positions
- Soccer – kicking the ball
- Running or cross country – running downhill
- Trauma – The os trigonum can also be created if a small bone is fractured or broken off of the back of the talus. This could occur with an injury, such as an ankle sprain. This small piece of bone can trigger os trigonum syndrome.
Os trigonum syndrome is often confused with Achilles tendinopathy or tendinitis because the pain is in a similar area. However the symptoms are different.
What are the symptoms of os trigonum syndrome?
There are several symptoms associated with os trigonum syndrome. These include
- Pain in the back outside part of the ankle when plantarflexing (pointing the foot down)
- Stiffness in the ankle
- Weakness in the ankle
- Swelling in the back of the ankle
- Decreased ability to plantarflex
- Pain when pushing off of the foot when walking, running, kicking, or dancing
Who should I see?
- Physical therapy – Conservative treatment is the first approach in treating os trigonum syndrome. This includes physical therapy. Your PT can help decrease the pain and swelling. Abnormal joint mobility, weakness, instability, and flexibility will be evaluated and addressed. Your PT will also assess your form during sport to help with any abnormalities that might be causing injury.
- Orthopedic physician – An orthopedist will be necessary if the condition is not responding to physical therapy. Anti-inflammatory medication or an injection might be needed to decrease the inflammation. Imaging can be used to determine if the extra bone is present or if other pathologies are present. Surgery to remove the os trigonum is an option if the condition is not improving with conservative treatment.
What can I do at home?
- Relative rest – Resting the area to decrease further pain and damage from occurring is one of the best ways to decrease treat os trigonum syndrome. Basically stay away from the activities that are causing pain until the pain and inflammation have subsided. This gives the area time to rest and heal. If you keep doing what is causing the inflammation, it is not going to get better. Swimming and biking would be a good alternative activities that do not put much stress through the ankle and foot.
- Ice – Ice can help decrease the pain and swelling at the ankle. Ice the painful area for 15 to 20 minutes at a time. I would recommend using an ice pack several times per day if the pain is constant or preventing you from participating in an activity. Ice immediately after activity.
- Strengthening the deep posterior compartment – Strengthening the muscles underneath the calf is very important. These muscles include the posterior tibialis, flexor digitorum longus, and the flexor hallucis longus. The flexor hallucis longus can also become irritated since it runs right next to the os trigonum. Strengthening this muscle will help decrease stress on the tendon. Below is video showing how to strengthen the muscles of the deep posterior compartment of the leg.
- Strengthening the hip and knee – It is important to strengthen the muscles around the knee and hip. All of these muscles work together to stabilize the ankle while squatting, running, cutting, and jumping. Using loop resistance bands, resistance bands, and ankle weights can increase the strength and difficulty of the exercises. See the videos below.
- Balance – Working on balance is important in strengthening the foot and ankle but also improving proprioception. Improving proprioception will help improve the overall stability of the ankle. See the video below.
- Bracing – Using a stability brace or ankle sleeve can be helpful to decrease pain and improve stabilization at the ankle. This is especially useful for those that have chronic ankle instability or who have suffered from previous ankle injuries.
- Compression socks – Compression socks can help decrease swelling and pain by improving circulation. It is important to put on compression socks after first waking up in the morning. This is usually when there is the least amount of swelling.
In review
- The ankle has two main joints.
- These are the talocrural and subtalar joints.
- The os trigonum is an extra bone at the back of the talus.
- It often fuses with the talus but in up to 15% of people, it remains a separate bone.
- Os trigonum syndrome is a condition that causes pain in the back of the ankle when plantarflexing (pointing) the foot.
- It is caused when the os trigonum is pinched between the calcaneus, talus, and tibia.
- There are two different ways to cause os trigonum syndrome.
- Overuse
- Trauma
- Symptoms of os trigonum syndrome include pain with plantarflexing (pointing) the foot.
- Conservative treatment including physical therapy is the first approach in treating the ankle.
- An orthopedist would be needed if the condition is not responding to physical therapy.
- There are things that you can do
- Relative rest
- Ice
- Strengthening the deep posterior compartment of the leg
- Strengthening the hip and knee
- Balance
- Brace
- Compression socks
As always, If you have questions about the content of this post or any other musculoskeletal questions, please e-mail me.
Additional resources
https://www.foothealthfacts.org/conditions/os-trigonum-syndrome
https://www.physio-pedia.com/The_Os_Trigonum_Syndrome
https://sportdoctorlondon.com/os-trigonum/
https://www.sportsmedreview.com/blog/os-trigonum-syndrome/