Sub-talar Joint Arthritis
The sub-talar joint (STJ) is the joint of your hindfoot that sits between the talus and calcaneus (heel bone). It is primarily involved in the moments of inversion and eversion – the ability to rotate your foot in and out. As with ankle joint arthritis, STJ arthritis occurs most commonly following previous trauma to the joint. It can also result from inflammatory arthritis, infective arthritis, and less commonly osteoarthritis. The most common preceding injuries leading to STJ arthritis are fractures of the calcaneus and talus.
Sub-talar arthritis is characterised by pain in the handfoot that is worse with standing and walking. In particular, it is aggravated with mobilising on uneven surfaces that involve inward and outward movements of the foot. Most commonly the pain locates to the areas below and in front of the malleoli, the bony prominences on either side of your ankle. The hollow just in front of the outside malleolus, called the sinus tarsi, is a common location for pain in STJ arthritis. The joint can also become swollen, making it difficult to put on normal footwear, with boggy swelling in the same areas that the pain localises.
The sub-talar joint actually incorporates 3 different joints – the talo-calcaneal joint (TCJ), talo-navicular joint (TNJ), and calcaneo-cuboid joint (CCJ). The TCJ sits under the ankle joint, with the TNJ and CCJ located in the midfoot. All 3 are involved in the movements of foot inversion and eversion, the ability to rotate the foot in and out. This movement is essential for stability when walking on uneven surfaces. The midfoot joints also contribute to up and down movements in the foot, and can compensate for loss of motion at the ankle joint proper.
Will my arthritis get better?
There is nothing that will reverse the process, and most patients show a slow progression of disease and worsening of symptoms. This does not always translate into a need for intervention – as the joint becomes more stiff, in some patients the pain can lessen. If the symptoms you are experiencing are not impacting on your quality of life, you do not require surgery. There may still be treatments available that can slow the progression of your arthritis, so it is still worthwhile discussing this with your local doctor on your next visit.
How quickly will my arthritis progress?
This is difficult to predict, as there is much variation from patient to patient. Inflammatory arthritis, including those due to infection, will tend to progress more quickly than post-traumatic arthritis.
How can I find out if I have STJ arthritis?
If you suspect you have a problem with your STJ, seek review with your local doctor. Diagnosis involves taking a detailed history and a thorough clinical examination, and where suspicion is high, performing imaging of the joint with plain X-rays. Sometimes a CT scan will also be ordered to give a 3D appreciation of the joint involvement and aid in surgical decision making. An MRI scan is also often used as it will show more clearly any damage to the articular cartilage surfaces, as well as more clearly display the surrounding soft tissues. An injection of cortisone (a corticosteroid) with local anaesthetic is often used as both initial treatment and to aid in diagnosis. When injected into the sub-talar joint, the anaesthetic component should completely resolve the pain, though only for a few hours. The steroid will help to decrease inflammation over the following few months. If there is no improvement in pain with the injection, your problem may be in another joint.
What non-surgical treatments are available?
As with all arthritic joints, there are a number of simple measures that can be trialled to help cope with the symptoms. These include:
- weight loss = even small losses decrease the load placed on this small joint.
- activity modification = avoiding those activities that cause pain.
- regular low impact exercise = maintain the range of motion in the joint without causing excessive load bearing on the joint.
- physiotherapy = can help by tailoring an exercise program to suit your needs.
- dietary supplements = there is no clear role for supplements in ankle arthritis.
- simple analgesics such as paracetamol and over-the-counter anti-inflammatory medications like ibuprofen and voltaren can help with pain control.
- splints and braces can be used to reduce motion in the ankle and foot further in order to alleviate pain.
- podiatry = a podiatrist can help in those who have foot alignment problems that can be improved with orthotics.
What surgical treatment options are available?
Generally speaking, arthroscopy is not an option for STJ pathology. The space is too narrow to access safely, and the results are less reliable than for other joints. There are also no reliable joint replacement options available for disease involving the sub-talar joint.
The gold standard treatment for advanced STJ arthritis remains joint arthrodesis (fusion). In this operation, the diseased cartilage surfaces are removed and the exposed bony surfaces joined together under compression using plates and screws. When these bones join together, there is no longer any movement at the site and the pain resolves. For the sub-talar joint, though all joined together, there are 3 distinct joints that can be involved, and thus 3 distinct areas that can be treated. A pure sub-talar arthrodesis involves joining only the talus to the calcaneus, and sparing the joints between the talus, navicular and cuboid in the midfoot. This preserves some rotation at the midfoot. A triple arthrodesis involves fusion of all 3 joints, and is used in more severe cases. As you can imagine, it leads to a great restriction of movement post-surgery.
Will I be able to do my usual activity after fusion surgery?
This will depend in part on whether an isolated STJ fusion is performed, or a triple arthrodesis is required. An STJ fusion will reduce the rotation of the foot, but as the TNJ and CCJ are left free, some motion is preserved, and thus function is increased. For a triple arthrodesis, the ankle joint will compensate slightly for the lost foot rotation, but this is limited. The main functional deficit will be with mobilising on uneven surfaces or any specific activity involving inversion or eversion of the foot. Dr Host will discuss with you the pros and cons of these procedures with you prior to any surgical decision being made.
How long will I need to be off my foot after fusion surgery?
As fusion surgery involves joining bones together, it can be considered much like a fracture. It will take 6 weeks for the bones to unite to the point of allowing some movement of the remaining foot, and 12 weeks before you can bear weight on the leg. Following surgery you will be treated in a plaster cast for 6 weeks. This will be changed to a CAM boot at the 6 week mark, and you will need to remain non weight bearing in that for a further 6 weeks. During the 6-12 week period, you will be allowed to remove the boot to begin gentle movements of the remaining joints of the foot.