Subtalar arthritis is characterized by pain in the hindfoot that is aggravated by standing and walking, particularly on uneven ground. It is likely to be associated with stiffness when attempting to move the foot from side to side. The location of the pain is commonly just below the level of the inside and outside ankle bones (medial and lateral malleoli). The most common cause of subtalar arthritis is a previous injury – usually a calcaneal fracture, or abnormal alignment of the heal bone. Non-operative treatment involves: 1) limiting the movement and loading through the subtalar joint by wearing comfort shoes, bracing the hindfoot and weight control; 2) activity modification such as decreasing standing and walking, particularly on uneven terrain; and 3) masking the pain by taking NSAIDs, if tolerated, to improve pain control. Surgery is indicated for subtalar arthritis that has failed non-operative treatment. Fusion of the subtalar joint is the most predictable surgical option, as it trades painful motion for relief of pain and improved function.
Patients with subtalar arthritis will complain of pain on one or both sides of the foot, just below the ankle bones (malleoli). This is commonly illustrated by the patient encircling the affected foot with their fingers, just below the level of the bony prominence on either side of the ankle (malleoli). The hollow just in front of the outside ankle bone (the sinus tarsi) is another common location of pain. The sinus tarsi is a space surrounded by the three contact areas between the talus and calcaneus, that comprise the subtalar joint. The subtalar joint is largely responsible for allowing the foot to accommodate uneven terrain by moving the hindfoot from side to side (inversion and eversion). Walking on uneven surfaces places a great deal of stress on the subtalar joint and may be difficult, if not impossible, to accomplish in patients with subtalar arthritis.
Most subtalar arthritis is caused by a previous trauma, usually a calcaneal fracture, although certain fractures involving the talar body may also cause subtalar arthritis. Other causes include rheumatoid arthritis, or the abnormal loading of the subtalar joint associated with malalignment of the heel bone (calcaneus). The load applied to the subtalar joint can be unevenly distributed in cases where the heel bone turns in (varus alignment seen with a high arched foot) or out (valgus alignment associated with a flat foot).
On examination, patients with subtalar arthritis will usually have noticeable stiffness when testing side-to-side motion. Additionally, this motion may cause pain in the locations described above. There may also be swelling that may bulge above the shoe line.
X-rays will reveal a loss of the subtalar joint space that is best seen on a lateral view of the foot, taken with the patient bearing weight (Figure 1).
A CT scan or MRI is sometimes indicated to identify the extent of the subtalar arthritis and to determine if there is any other source of pain (ex. ankle arthritis, posterior tibial tendonitis, peroneal tendonitis, etc.)
Occasionally, a diagnostic injection of local anesthetic (ex. lidocaine) will be performed to get some sense of how much pain is originating from the subtalar joint. In some cases, the injection may be given with aid of ultrasound, fluoroscopy (mini x-ray), or CT scan, to ensure that the anesthetic agent is accurately placed. The lidocaine will only last a few hours and when it wears off the pain may actually be worse for a short while. However, if immediately after the injection the patient has a significant relief of pain for a few hours, this suggests that most of the symptoms are coming from the area that was injected – in this case the subtalar joint.
Non-operative treatment focuses on limiting the amount of loading and movement at the subtalar joint, and masking the pain. Non-operative treatment involves some trial and error on the part of the patient to see what strategies are most effective. Non-operative treatments include:
Operative treatment is usually reserved for extensive subtalar arthritis that has failed non-operative management. Occasionally patients will be noted to have an isolated area of damage to the subtalar joint, or will have a loose body which can addressed by cleaning out (debriding) the subtalar joint, either arthroscopically or more commonly by opening the joint. However in most instances, patients with subtalar arthritis have lost significant cartilage and need to have the subtalar joint fused (Figure 2).
A subtalar fusion is not to be confused with a subtalar arthroresis (placing a plug in the subtalar joint), which is not appropriate for treating subtalar arthritis.