Subtalar Arthritis

Subtalar arthritis is degenerative disease of the subtalar joint, most commonly after an intra-articular calcaneal fracture. The joint is a complex of three facets, anterior, middle and posterior, between the talus and the calcaneus, and it supplies the hindfoot inversion and eversion that let the foot walk on uneven ground.

Who. Most cases follow a calcaneal or talar fracture. Post-traumatic disease peaks at 40-60 years, and men outnumber women 3:1, which reflects the trauma pattern. Primary osteoarthritis, the inflammatory arthropathies (rheumatoid, psoriatic, seronegative) and tarsal coalition make up the rest of the aetiological classification below.

What it costs. Subtalar motion is essential to normal gait mechanics. Without it the hindfoot is stiff and shock absorption is reduced. Loss of this motion also causes compensatory stress at the adjacent joints, the ankle and midfoot, with a risk of secondary arthritis there over time. It significantly impairs function on slopes and irregular surfaces.

The three facets. The posterior facet is the largest, the middle facet sits medially on the sustentaculum tali, and the anterior facet, the smallest, lies on the talar head as part of the talocalcaneonavicular complex. This anatomy governs surgical planning and the choice of approach; the table gives each facet's share of the load and its clinical significance.

Motion. The joint provides mainly inversion and eversion, an arc of 20-30° in total. That arc and the load shares in the table are single figures for a joint that does not behave singly: the facets contribute differently across stance, and inversion and eversion are coupled with talonavicular, calcaneocuboid, ankle and midfoot motion. Compare the two sides and the patient's function rather than quote one arc or load percentage. What the motion does:

• With ankle dorsiflexion, subtalar eversion unlocks the midfoot
• With ankle plantarflexion, subtalar inversion locks the midfoot
• It dampens impact forces at heel strike
• It lets the foot conform to uneven surfaces

View larger

The post-traumatic pathway. An intra-articular calcaneal fracture leaves an incongruous joint surface. The cartilage is damaged both directly at injury and by abnormal loading, and a malunion alters the mechanics further and accelerates degeneration. A Bohler angle below 20° correlates with arthritis risk, and symptoms typically develop 1-5 years after injury.

What the fracture leaves behind. Prior calcaneal or talar injury can add height loss, widening, translation, varus or valgus malalignment, a bone void or avascular bone, and adjacent-joint disease to the arthritis itself. These features, not the trauma label alone, drive the reconstruction. Posterior-facet collapse in particular can leave compromised perfusion and a subchondral void after reduction, which influences the biology of any later fusion.

View larger

Primary, inflammatory and other pathways. Primary osteoarthritis is rare in isolation and usually associated with hindfoot malalignment or other hindfoot pathology. Inflammatory disease includes rheumatoid, psoriatic and ankylosing spondylitis arthropathy. A tarsal coalition imposes chronic abnormal stress, and a cavus or planovalgus foot overloads the joint mechanically. Their progression often involves multiple hindfoot joints.

Rammelt-Zwipp Types I–V are a descriptive framework for escalating calcaneal-malunion components:

• Type I: arthritis without material malalignment.
• Type II: adds hindfoot varus/valgus.
• Type III: adds height loss and altered talar inclination.
• Type IV: adds lateral calcaneal translation/fibular abutment.
• Type V: adds talar/ankle-mortise malalignment.
• Bone status can be described separately as malunion, nonunion or osteonecrosis/infection.

The classification prompts a checklist; it does not prescribe one operation per number. Fusion, bone block, osteotomy, lateral-wall/peroneal work, ankle procedure and staging follow measured deformity, symptoms, biology and reconstructability.

History. Pain sits in the sinus tarsi, over the lateral hindfoot, or deep in the heel, and is worse on uneven ground, on stairs and with prolonged walking. Morning stiffness improves with activity at first. Descending stairs hurts because it loads the foot in plantarflexion. Ask about a previous calcaneal or talar fracture.

Function. Patients report difficulty with:

• Walking on slopes and uneven surfaces
• Running, significantly limited or impossible
• Work that demands prolonged standing or manual labour
• Hiking and sport
• An antalgic limp that avoids inversion and eversion

Inspection. Stand the patient and assess hindfoot alignment (varus, valgus or neutral), then watch the gait for stiffness and an antalgic pattern. Look for the scars of calcaneal fracture fixation. Fullness over the sinus tarsi and lateral hindfoot oedema are common.

Palpation. Tenderness is focal in the sinus tarsi, lateral to the talus and anterior to the lateral malleolus. The subtalar joint line is palpable posteriorly and tender on deep palpation. A healed fracture may leave the calcaneus widened, with a lateral prominence.

Motion. Compare inversion, eversion and the hindfoot response with the opposite side and with the adjacent joints; the normal arc varies, and pain or guarding can mimic rigidity. Test the ankle and the midfoot, including Chopart joint mobility, separately, because combined pathology changes the procedure and the prognosis. Then the special tests:

• Subtalar stress test - stabilise the talus and move the calcaneus into inversion and eversion; pain and restriction indicate pathology
• Anterior drawer - rules out ankle instability as the pain source
• Talonavicular stress - looks for combined pathology, which bears on whether a triple fusion is needed

Radiographs. Weight-bearing films come first, and the views are tailored to the deformity:

• AP, lateral and oblique foot - subtalar joint space, calcaneal morphology and the adjacent joints
• AP ankle and hindfoot-alignment views - alignment
• Broden views - profile the posterior facet
• Harris axial - helps with width and alignment

Neither the Broden nor the Harris view is universally definitive; both are adjuncts.

CT. Multiplanar weight-bearing or conventional CT maps the joint surfaces, calcaneal height, width and translation, bone void and avascularity, coalition, osteophytes, impingement, the adjacent joints and, after surgery, fusion contact and union.

View larger

View larger

MRI. Reserve it for a question it can answer and that changes care: marrow oedema, an occult stress injury, sinus-tarsi, ligament or tendon pathology, infection, or another soft-tissue differential.

View larger

Diagnostic injection. An image-guided local anaesthetic injection can modify pain and help localise the source in a complex hindfoot. Confirm intra-articular placement with fluoroscopy or ultrasound as appropriate, and record the immediate change in a specific painful task. Contrast and anaesthetic spread, and mixed or multi-joint disease, limit its specificity, so a partial or absent response is informative but does not prove or exclude the joint. There is no universal relief threshold: 75% relief does not confirm the diagnosis.

Lateral/posterior hindfoot pain is non-specific. Build concordance across history, examination, weight-bearing alignment and targeted CT/MRI; use image-guided block only when it adds useful localization.

View larger

View larger

View larger

Calcaneal malunion may combine subtalar cartilage loss with height loss/talar dorsiflexion, widening/lateral-wall or peroneal impingement, translation, varus/valgus and shoe-fit problems.

• Height/talar declination: distraction bone block is considered when restoring height is expected to relieve anterior ankle mechanics and improve alignment—not whenever height is reduced.
• Lateral wall/translation: decompression, peroneal treatment and/or osteotomy follow demonstrated impingement and translation.
• Alignment: correct clinically meaningful varus/valgus while avoiding overcorrection.
• Biology: avascular posterior-facet fragments, voids, infection/nonunion and soft tissue change graft/fixation/staging.

In-situ fusion may remain appropriate when these extra-articular/deformity components are absent or clinically unimportant.

Infection is reported at 1-3% superficial and less than 1% deep. Ongoing pain after fusion may come from adjacent-joint arthritis through ankle or midfoot overload, and a varus or valgus malunion adds to that stress.

View larger

Aftercare follows the operation, the biology and the fixation:

• Protect the wound and soft tissue, manage swelling and pain, and individualise VTE prophylaxis
• Set immobilisation and weight-bearing from bone contact, structural graft, fixation, neuropathy, revision or infection, and the patient's reliability
• Use weight-bearing radiographs and CT selectively when clinical or radiographic union is uncertain; do not schedule CT solely by week number
• Progress loading when pain, swelling, alignment, fixation and bridging bone support it
• Preserve ankle, midfoot, toe, strength and gait capacity while the subtalar joint is protected
• Continue smoking, metabolic, nutritional and infection optimisation through fusion

Return to work and sport depends on union, footwear, terrain and the demands of the task. There is no universal three- or six-month date.

Pain and function usually improve after successful fusion in appropriately selected patients, but reported union and pain percentages vary with aetiology, deformity, technique, definition and follow-up. Triple fusion cannot be assumed to relieve more pain, or to unite less reliably, than isolated fusion without comparable populations.

Measuring the result. Record patient-reported pain and function, footwear, capacity on uneven ground, alignment, union and contact, and the adjacent joints. Workers' compensation status should not be presented as a biological predictor without contextual evidence.

No dedicated registry or global guideline establishes subtalar-fusion indications, injection thresholds, constructs or rehabilitation. Evidence is mainly retrospective series plus calcaneal-fracture/malunion literature.

Consent is individualized: residual pain, motion/terrain trade-off, union/nonunion, malposition, nerve/wound/infection/hardware, adjacent-joint symptoms, VTE plan and possible revision. Do not quote ankle-fusion odds or fixed subtalar percentages as personal certainty, and do not require six months or a positive block as documentation rituals.

Related pages: Calcaneal Fractures, Talus Fractures, Talar Body Fractures, Lateral Process Talus Fractures, Posterior Process Talus Fractures, and Subtalar Dislocations.