Several tendons cross the ankle joint and are essential to normal foot and ankle function. The peroneal tendons (peroneus longus and brevis) run along the outer ankle and stabilize against inversion; the posterior tibial tendon runs along the inner ankle and supports the arch. Tears of these tendons — whether acute or degenerative — are a significant and often underdiagnosed cause of chronic ankle pain and dysfunction. The Achilles tendon, covered separately, is the largest tendon of the ankle complex.
Ankle tendon tears frequently occur alongside or are mistaken for ankle ligament sprains, particularly peroneal tendon injuries following inversion trauma. Posterior tibial tendon dysfunction is closely linked to progressive flatfoot deformity and must be distinguished from sinus tarsi syndrome and plantar fasciitis in patients with medial ankle and arch pain.
Causes
Peroneal tendon tears
- Inversion ankle sprain: The most common mechanism — forceful inversion of the ankle loads the peroneal tendons suddenly, causing longitudinal splitting or avulsion of the peroneus brevis tendon at the fibular groove. Many peroneal tears are initially misdiagnosed as simple ankle sprains.
- Chronic overuse: Repetitive loading in runners and jumping athletes causes progressive tendinosis and longitudinal tearing, particularly of the peroneus brevis.
- Anatomical predisposition: A shallow or convex fibular groove and a low-lying peroneus brevis muscle belly increase tendon instability and tear risk.
- Peroneal tendon subluxation: Disruption of the superior peroneal retinaculum allows the tendons to snap out of the fibular groove, causing tearing from repeated dislocation.
Posterior tibial tendon tears
- Degenerative tendinopathy: The most common cause — gradual age-related degeneration of the tendon, accelerated by overuse, obesity, hypertension, and diabetes. Progressive weakening leads to partial then complete tearing.
- Acute trauma: A sudden forceful eversion or direct blow can acutely rupture the posterior tibial tendon, though this is less common than degenerative tearing.
- Inflammatory conditions: Rheumatoid arthritis and seronegative arthropathies can cause synovitis and weakening of the tendon sheath.
- Biomechanical factors: Flat feet increase the mechanical load on the posterior tibial tendon; obesity significantly accelerates degenerative changes.
Symptoms
Peroneal tendon tear
- Lateral ankle pain and swelling, posterior to the fibula
- Pain and weakness with eversion (turning the foot outward) against resistance
- A sensation of snapping or popping behind the outer ankle during movement (suggests subluxation)
- Chronic lateral instability that does not fully resolve after ankle sprain treatment
Posterior tibial tendon tear
- Medial ankle pain and swelling along the inner ankle and arch
- Progressive flattening of the foot arch (acquired flatfoot deformity)
- Inability to perform a single-leg heel rise — the key functional test
- "Too many toes" sign — when viewed from behind, more toes are visible on the affected side due to forefoot abduction
- Pain that worsens with prolonged standing and walking
Diagnosis
Physical examination identifies the affected tendon based on location of tenderness, pain with resisted motion testing, and functional deficits such as inability to perform a single-leg heel rise (posterior tibial) or weakness with eversion (peroneal). The Thompson test is used specifically for the Achilles tendon.
MRI is the definitive imaging study for ankle tendon tears and is essential for accurate diagnosis and surgical planning. MRI characterizes the type and extent of tendon injury — distinguishing tendinosis (degeneration without tearing), partial longitudinal splitting, and complete rupture — and evaluates the tendon sheath for synovitis or fluid. For peroneal tendons, MRI identifies the classic "C-shaped" split tear of the peroneus brevis wrapping around the peroneus longus. For the posterior tibial tendon, MRI grades the tear and assesses the degree of associated flatfoot deformity and subtalar joint involvement. This information directly determines whether conservative or surgical management is appropriate.
Classification
Posterior tibial tendon dysfunction (PTTD) is graded using the Johnson-Strom classification:
- Stage I: Tendinopathy and synovitis without deformity. Tendon intact but painful and swollen. Heel rise possible.
- Stage II: Partial or complete tear with flexible flatfoot deformity. Single-leg heel rise weak or absent.
- Stage III: Rigid flatfoot deformity with fixed hindfoot valgus. Subtalar joint arthritis present.
- Stage IV: Stage III with additional ankle joint involvement and valgus tilt of the talus.
Treatments
Conservative treatment (Stage I PTTD and partial peroneal tears):
Immobilization in a walking boot for 4–6 weeks to allow acute inflammation to resolve, followed by a structured physical therapy program emphasizing tendon strengthening and proprioception. Custom orthotics with medial arch support and hindfoot posting offload the posterior tibial tendon effectively. NSAIDs reduce pain and inflammation. Corticosteroid injections into the tendon sheath — not the tendon itself — provide short-term relief but are used cautiously given the risk of tendon weakening.
Surgical treatment for peroneal tendon tears:
Longitudinal peroneus brevis tears are repaired by tubularization (suturing the split tendon back into a cylindrical shape) or debridement of frayed tissue. In cases of peroneal tendon subluxation, the superior peroneal retinaculum is repaired and the fibular groove deepened. Most patients return to full activity within 4–6 months with appropriate rehabilitation.
Surgical treatment for posterior tibial tendon tears (Stage II):
The gold standard is flexor digitorum longus (FDL) tendon transfer combined with a medial displacement calcaneal osteotomy to realign the hindfoot. This restores active arch support while correcting the biomechanical deformity driving the condition. In younger or lower-demand patients, isolated tendon repair may be considered for acute complete tears.
Advanced reconstruction (Stage III–IV):
Rigid deformity with arthritis requires hindfoot fusion procedures — subtalar, double, or triple arthrodesis — to correct alignment and eliminate pain. Ankle joint involvement (Stage IV) may require additional ankle realignment or replacement procedures. These are complex reconstructions with prolonged recovery but provide reliable pain relief when simpler procedures are no longer viable.
Rehabilitation (all patients):
Structured physical therapy is essential after both conservative and surgical management, focusing on progressive tendon loading, peroneal or posterior tibial strengthening, proprioceptive training, and gait retraining. Return to sport or full activity typically requires 4–6 months following surgical repair.
Get an MRI to Confirm Your Diagnosis
Before surgical planning or starting treatment, a clear MRI diagnosis ensures the right path forward. First Look MRI offers self-pay Foot and Ankle MRI scans — no doctor's order or insurance required — at our locations in Georgia, Texas, and Colorado.