Posterior tibial tendinopathy is one of the more under-recognised running injuries in clinical literature and one of the more frequently mistaken in running culture. It is often labelled as plantar fasciitis, generic medial arch pain, or shin splints. The differential matters because the management for each diverges significantly. This article reviews what the research says about the pathology, the validated diagnostic patterns, and the causal mechanisms in distance runners.
Where the evidence is strong, I will cite specific studies. Where it is weaker, I will say so. The aim is to give you a defensible picture of what this condition actually is, what it is not, and what we know about its causes.
What posterior tibial tendinopathy is, and isn't
The posterior tibial tendon arises from the muscle of the same name, courses behind the medial malleolus, and inserts primarily on the navicular tuberosity with smaller slips to other midfoot bones. Its functional role is to invert the foot, plantarflex the ankle, and provide dynamic support to the medial longitudinal arch during stance. Pathology of this tendon disrupts arch support, which is why advanced cases produce progressive flatfoot deformity.
The shift from "tendinitis" to "tendinopathy"
Histological work by Mosier et al. (1998), Goncalves-Neto et al. (2002), and subsequent reviews demonstrated that chronic posterior tibial tendon pain is rarely characterised by classical inflammatory infiltrate. The pathology is degenerative: disorganised collagen, increased ground substance, neovascularisation. The terminology shift from "tendinitis" to "tendinopathy" reflects this. The clinical implication is that anti-inflammatory protocols are not the first-line intervention they were once assumed to be.
Johnson and Strom staging
The Johnson and Strom (1989) classification remains the standard clinical staging. Stage 1: tenosynovitis with normal alignment. Stage 2: tendon degeneration with flexible flatfoot deformity. Stage 3: rigid flatfoot. Stage 4: rigid flatfoot with ankle involvement. Most runners present with Stage 1 or early Stage 2. Recognising the stage matters because Stage 1 responds well to load management and progressive loading, while later stages require more involved orthotic management and sometimes surgical referral.
The clinical pattern
Several presenting features cluster reliably in clinical case series.
The pain location
Medial ankle pain, immediately behind and below the medial malleolus, sometimes radiating into the medial midfoot toward the navicular tuberosity. The pain is often described as a deep ache rather than a sharp pain. Conti et al. (1992) and subsequent imaging studies confirm the location as a specific signal.
The activity pattern
Pain that worsens with running, particularly during long runs and uphill segments. Pain that lingers after running for hours rather than minutes. Morning stiffness in the medial ankle. Pain on the single-leg calf raise on the affected side. Difficulty rising onto the toes from a single-leg stance is highly specific in moderate-to-advanced cases.
The differential
Plantar fasciitis (medial heel pain on first morning steps, not behind the medial malleolus). Tarsal tunnel syndrome (numbness or tingling distribution, neurological signs). Medial tibial stress syndrome ("shin splints," pain higher on the medial tibia). Navicular stress fracture (point tenderness at the dorsal navicular, often with focal swelling). The diagnostic differentiation rests on clinical examination plus, where indicated, ultrasound or MRI.
What the research identifies as causes
Several factors recur in the literature as associated with onset and risk.
Sudden increases in training volume
The acute:chronic workload framework (Gabbett, 2014 onwards) applies here as for other soft-tissue conditions. Cohort studies of distance runners identify rapid weekly volume increases (greater than 15 percent from a four-week rolling average) as associated with elevated soft-tissue injury risk. Retrospective surveys of runners with posterior tibial tendinopathy consistently identify a marathon training block or a sudden long-run distance jump in the 4 to 8 weeks before symptom onset.
Hill running and downhill loading
Uphill running increases push-off load through the calf and posterior tibial tendon. Downhill running increases eccentric loading on the medial structures of the foot and ankle. Burns et al. (2005) and biomechanical studies of foot kinematics support both as recognised contributors. Abrupt introduction of hill-pattern courses or downhill segments is a recurring trigger in clinical case series.
Footwear transitions
Transitions from supportive trainers to minimalist or zero-drop shoes increase load on the posterior tibial tendon, which carries more of the arch support burden as external support reduces. Ridge et al. (2013) demonstrated increased intrinsic foot loading with minimalist transitions. The recommendation is gradual transition over 12 weeks rather than rapid switches.
The biomechanical contributors
Several biomechanical patterns appear in retrospective analyses of runners with posterior tibial tendinopathy.
Excessive pronation
Hintermann and Nigg (1998), Kohls-Gatzoulis et al. (2004), and subsequent biomechanical work demonstrate that excessive subtalar pronation increases load on the posterior tibial tendon during stance. Foot type is a non-modifiable risk factor, but the dynamic response can be addressed through orthotics, footwear, and intrinsic foot strengthening.
Calf tightness and posterior chain stiffness
Reduced ankle dorsiflexion is associated with increased pronation and increased posterior tibial loading (DiGiovanni et al., 2002; Riddle et al., 2003). The intervention is straightforward: progressive calf stretching combined with loaded eccentric calf work.
Intrinsic foot weakness
McKeon et al. (2015) and subsequent work demonstrate that intrinsic foot muscle strength influences dynamic foot posture during stance. Whether weakness causes posterior tibial tendinopathy or co-exists with it is debated, but the rehabilitation response to short-foot exercises and intrinsic strengthening is reasonable.
Behavioural patterns that increase risk
Beyond training load and biomechanics, several behaviours appear associated with onset.
Inadequate calf and posterior tibial strengthening
Distance runners frequently under-load the calf complex. The posterior tibial tendon is a major component of dynamic arch support, and its capacity scales with progressive loading. Runners who run high mileage without calf and intrinsic foot strength work are over-represented in clinical case series.
Returning from injury too quickly
Recurrence patterns are well documented. Runners who return to full training before completing structured rehabilitation experience higher recurrence rates. Silbernagel et al. (2007) document this pattern for Achilles tendinopathy, and similar patterns appear for posterior tibial tendinopathy in case series.
Body composition factors
Obesity is identified as a risk factor in non-running cohorts (Holmes and Mann, 1992; Kohls-Gatzoulis et al., 2004). In distance runners, where overall BMI tends to be lower, the relationship is less established but plausible: greater body mass increases tendon load per step.
Diagnosis: clinical and imaging
The diagnosis is primarily clinical. Imaging is reserved for unclear cases or to guide management in advanced stages.
Clinical examination
A sports physiotherapist or podiatrist will perform: palpation along the tendon path, single-leg calf raise test (most predictive), "too many toes" sign in stance, resisted inversion strength assessment, and gait observation. The pattern of findings establishes the diagnosis in most cases.
Ultrasound
Ultrasound is sensitive for tendon thickening, neovascularisation, and tenosynovitis. It is increasingly the first-line imaging in sports clinics. Its principal advantage is dynamic assessment.
MRI
MRI is reserved for cases where the clinical picture is unclear, where stress fracture must be excluded, or where surgical planning is required. It is not routinely needed for diagnosis.
What to do this week
If the pattern matches, the immediate steps are clear. Reduce running volume by 30 to 40 percent. Cut hills and downhill segments. Switch to a supportive stability shoe. Begin progressive calf and posterior tibial loading from the STRIDD exercise library. Read the STRIDD injuries hub for the wider triage. Read the STRIDD recovery guide for the structured return-to-run framework.
If the pattern does not match cleanly, consult a sports physiotherapist before self-managing. The differential diagnoses (plantar fasciitis, tarsal tunnel syndrome, navicular stress fracture) require different management. For balanced training-load plans during the rebuild, use the plan generator. For more clinical guides, visit the Running Lab.