Running with Accessory Navicular Pain: A Study on Conservative Treatment

Accessory Navicular Syndrome (os tibiale externum) is one of the clinically highly concerning sports injuries among endurance and competitive athletes, with its pathology primarily located on the medial aspect of the foot. Epidemiological studies indicate that the incidence of this injury in the active athletic population is not negligible, and it is closely related to training load, biomechanical alignment, and individual recovery capacity. According to pooled data from BJSM and AJSM over the past decade, overuse injuries account for approximately 60–70% of endurance sports injuries, and accessory navicular syndrome is a recurring representative among them. Research indicates significant differences in incidence by sex, age, and sport discipline, highlighting the importance of individualized assessment.

In Taiwan, with the flourishing of全民運動風氣 and the rapid growth of marathons, cycling, and triathlon events, outpatient visits for accessory navicular syndrome have been rising year by year. Urban athletes often train at high frequency on hard surfaces, and the subtropical humid heat climate leads to earlier fatigue and insufficient recovery, making repetitive loading on the medial foot a significant issue in local sports medicine. This article will provide an in-depth analysis covering injury mechanisms, diagnostic assessment, treatment comparisons, progressive rehabilitation, prevention strategies, and local applications in Taiwan, integrating the latest academic evidence to help readers establish a scientific understanding.

Injury Mechanism Analysis

The core pathomechanism of accessory navicular syndrome can be summarized as “traction between the accessory navicular and the posterior tibial tendon.” From a biomechanical perspective, the medial foot experiences repetitive and high-peak mechanical loads during exercise. When the intensity of a single load or the cumulative load volume exceeds the tissue’s repair capacity, microdamage gradually accumulates and eventually surpasses the tissue tolerance threshold, resulting in clinically visible injury. This “load–capacity imbalance” model has become the core framework in modern sports medicine for understanding overuse injuries.

Research by Leonard ZC & Fortin PT (2010). Foot Ankle Int, using imaging and biomechanical analysis, revealed that imbalance at any link in the kinetic chain alters the load distribution on the medial foot. Proximal control deficits (e.g., poor hip and trunk stability) or distal alignment abnormalities (e.g., excessive foot pronation) can transmit forces through mechanical pathways, subjecting target tissues to non-physiological shear and compressive stresses. This “cascading malalignment” concept emphasizes that pain at a single site is often the terminal manifestation of dysfunction throughout the entire kinetic chain.

At the anatomical and tissue level, Kiter E et al. (2000). Foot Ankle Int further noted that repetitive loading induces the release of local inflammatory mediators, disorganization of collagen fiber alignment, and, in the chronic phase, neovascularization with accompanying nerve ingrowth. This explains why chronic lesions present primarily with pain rather than typical inflammatory signs. Histological studies show that the essence of chronic overuse pathology is “degeneration” rather than simple “inflammation.” This conceptual shift directly influences treatment strategy—moving from anti-inflammatory approaches toward progressive loading that promotes tissue remodeling.

The role of neuromuscular control cannot be overlooked. Knapik DM et al. (2019). Sports Health, using electromyography and motion analysis, confirmed that injured individuals often exhibit altered muscle activation timing, increased co-contraction of antagonist muscles, and delayed proprioceptive feedback. These maladaptive neural changes reduce dynamic stability during movement, creating a vicious cycle of “injury—worsening control—reinjury.” Furthermore, fatigue amplifies these deficits: when muscles fatigue, their shock-absorbing capacity declines, and load is shifted to passive structures (bone, ligaments, tendon attachment sites), accelerating microdamage accumulation.

In summary, accessory navicular syndrome is not a single-factor disease but the result of the interaction of multiple factors: “training load, biomechanical alignment, neuromuscular control, tissue repair capacity, and psychosocial stress.” Understanding this multifactorial model is a prerequisite for accurate diagnosis and effective intervention.

Diagnostic and Assessment Methods

The diagnosis of accessory navicular syndrome should be based on triangulation involving a thorough history, systematic physical examination, and appropriate imaging confirmation. History-taking must clarify the temporal pattern of pain onset, its relationship to training load, aggravating and relieving factors, and any previous injury history. Typical overuse injuries present with a “progressive, activity-related” pain pattern, whereas sudden severe pain should raise suspicion for acute structural damage or stress fracture.

On physical examination, clinicians should perform local palpation to localize tender points, assess joint range of motion, muscle strength, and flexibility, and conduct targeted provocation tests to reproduce symptoms. Dynamic assessments such as single-leg squats, jump landings, and running gait analysis can reveal dynamic alignment abnormalities (e.g., dynamic valgus, pelvic drop) that static examinations may miss. Leonard ZC & Fortin PT (2010). Foot Ankle Int and Cha SM et al. (2013). J Foot Ankle Surg both emphasize that the diagnostic validity of any single test is limited; combining multiple tests with functional performance is necessary to improve diagnostic accuracy and reduce misdiagnosis rates.

The choice of imaging modality should be guided by the clinical question, avoiding over-investigation. The following table summarizes the characteristics of commonly used imaging and assessment tools:

Imaging/Assessment Tool	Primary Use	Sensitivity Overview	Clinical Notes
Plain X-ray	Exclude fractures, calcifications, and bony structural abnormalities	Low for early soft tissue pathology	First-line screening, low cost
Ultrasound (US)	Real-time assessment of tendon and soft tissue in accessory navicular syndrome; allows dynamic testing	High for superficial lesions	Operator-dependent; can guide injections
Magnetic Resonance Imaging (MRI)	Assess soft tissue, bone marrow edema, and occult lesions	High for both bone and soft tissue	Expensive; gold standard for complex cases
Bone scan	Detect bone metabolic activity and early bone response	Sensitive for bone response, low specificity	Increasingly replaced by MRI

Image interpretation must adhere to the “clinical–imaging concordance principle”: abnormal signals on imaging are not necessarily the source of symptoms, as tendon degeneration or cartilage changes are also common in asymptomatic populations. Kiter E et al. (2000). Foot Ankle Int cautions that over-reliance on imaging may lead to unnecessary interventions and patient anxiety. Therefore, the ultimate goal of assessment is not merely to name the lesion but to identify correctable sources of load and functional deficits, and based on that, formulate an individualized treatment and rehabilitation plan. Grading systems (e.g., by symptom severity or imaging stage) can aid in prognosis and return-to-play timeline planning.

Comparison of Treatment Options

Treatment for accessory navicular syndrome should follow a stepwise principle of “conservative first, invasive later.” Exercise therapy is the core first-line approach, supplemented by pain management and activity modification; invasive treatments are reserved for cases where conservative treatment has failed or where there is clear structural damage. In recent years, high-quality RCTs consistently support progressive loading exercise as the most effective intervention for most overuse injuries. A systematic review by Leonard ZC & Fortin PT (2010). Foot Ankle Int showed that functional, progressive-loading-based exercise programs were superior to passive treatments in pain and functional improvement, with long-term maintenance of effects.

The following table compares the mechanisms, evidence levels, and indications of the main treatment options:

Treatment Option	Mechanism of Action	Evidence Level	Indication
Exercise therapy (progressive loading)	Promotes tissue adaptation, restores strength and control	High (supported by multiple RCTs)	First choice at all stages; long-term cornerstone
Manual therapy	Short-term pain relief, improves joint mobility	Moderate	Adjunct in the acute phase
Extracorporeal shock wave therapy (ESWT)	Mechanotransduction promoting vascular and cellular repair	Moderate	Chronic refractory lesions
Injection therapy (PRP/steroids)	Growth factors or anti-inflammatory effects	Low to moderate, controversial	Judicious use after conservative failure
Surgery	Repair or decompress structural lesions	Depends on the lesion	Failure of 3–6 months of conservative treatment or structural damage

Regarding injection therapy, Knapik DM et al. (2019). Sports Health and related meta-analyses present divergent results: steroid injections may provide short-term pain relief, but in the medium to long term, they may be detrimental to tissue healing and even increase recurrence; evidence for platelet-rich plasma (PRP) is highly heterogeneous, with some studies showing benefit for specific tendinopathies, but overall efficacy still requires more rigorous trials. Extracorporeal shock wave therapy (ESWT) shows moderate evidence for chronic refractory lesions and can be considered when conservative treatment plateaus.

Surgery is indicated only for clear structural damage (e.g., complete rupture, unstable osteochondral lesions) or when long-term conservative treatment has failed. Cha SM et al. (2013). J Foot Ankle Surg notes that even for lesions traditionally leaning toward surgery, an increasing number of long-term follow-up studies show that structured conservative treatment can achieve functional outcomes comparable to surgery while avoiding surgical risks. Therefore, shared decision-making is especially important in treatment selection, taking into account athletic demands, timeline, and personal preferences.

Progressive Rehabilitation Protocol

Rehabilitation for accessory navicular syndrome should be centered on the principle of “progressive loading under pain monitoring.” Clinically, a 0–10 numeric pain rating scale is commonly used, allowing pain during exercise and within 24 hours after exercise to not exceed 3/10, and morning stiffness not to worsen, as indicators for safe progression. Rehabilitation is typically divided into four phases, and each phase must meet clear criteria-based progression standards before advancing, rather than relying solely on time.

The following is the phased rehabilitation framework:

Phase	Goal	Representative Interventions	Progression Criteria
Phase 1: Pain control and protection	Reduce irritation, maintain baseline mobility	Relative rest, isometric contractions, activity modification	No significant pain during daily activities
Phase 2: Restore strength and mobility	Rebuild strength, endurance, and joint control	Progressive resistance training, eccentric training, proximal strengthening	Affected side strength ≥80% of the healthy side
Phase 3: Functional and sport-specific strengthening	Restore power, elasticity, and movement quality	Plyometric training, single-leg stability, running form re-education	Good symmetry on functional tests, no pain
Phase 4: Return to sport and reinjury prevention	Gradually return to sport-specific training volume	Progressive return to running/cycling volume, load monitoring	Pass return-to-sport testing, load tolerance achieved

Phase 1 emphasizes “relative rest” rather than complete immobilization—complete inactivity accelerates muscle atrophy and tissue deconditioning. Isometric contractions have been shown to provide immediate pain relief and maintain strength in many tendinopathies. Phase 2 introduces progressive resistance and eccentric training to promote collagen remodeling and strengthening of the muscle–tendon unit. Phase 3 adds plyometric and sport-specific movements to rebuild tissue tolerance to high-speed, high-impact loads. Phase 4 uses quantified load monitoring (e.g., weekly training volume changes, acute:chronic workload ratio) to ensure a smooth return process and avoid recurrence from rushing. The entire process should be individualized, with regular tracking of outcomes using objective metrics (strength, jump tests, movement quality).

Prevention Training Strategies

The key to preventing accessory navicular syndrome lies in two pillars: “managing training load” and “enhancing biomechanical resilience.” Regarding training load management, avoiding sudden spikes in weekly training volume is the primary principle. Research generally recommends that weekly training volume increases should not exceed approximately 10%, and the acute:chronic workload ratio (ACWR) can be used to maintain a relatively safe range, balancing adaptation and risk control. Overtraining and insufficient recovery weaken tissue repair capacity and are common upstream factors in many overuse injuries.

Building biomechanical resilience requires targeting the entire kinetic chain. The following are specific, evidence-based preventive exercise directions:

1. Proximal stabilization strengthening: Strengthen hip abductors, hip extensors, and trunk core muscles to improve dynamic alignment and reduce compensatory loading—this is a common foundation for preventing lower extremity overuse injuries.
2. Eccentric and progressive resistance training: Eccentric loading has been shown to enhance tendon and muscle tolerance and is particularly effective for preventing muscle and tendon pathology.
3. Movement quality re-education: Improve running form (e.g., moderately increasing cadence, avoiding overstriding) and cycling posture (appropriate saddle and handlebar setup) to reduce peak loads per stride/revolution.
4. Maintaining flexibility and mobility: Perform dynamic stretching and mobility training for key tight muscle groups to ensure smooth mechanical transmission.
5. Progressive adaptation and periodization: Structure training with periodization, incorporating deload weeks to allow adequate tissue repair and supercompensation.

It is worth emphasizing that prevention programs only work if adherence is achieved. Integrating preventive exercises into the regular warm-up or strength routine and presenting them in a simple, executable format is key to improving long-term compliance. Coaches and athletes should foster a culture of “listening to body signals,” treating minor discomfort as an early warning to adjust training rather than ignoring it or pushing through.

Local Applications in Taiwan

Taiwan’s geography, climate, and event environment have unique influences on the occurrence and management of accessory navicular syndrome. Climatically, Taiwan’s summers are hot and humid, causing core body temperature to rise quickly during exercise and increasing dehydration risk. Earlier fatigue leads to decreased neuromuscular control, indirectly increasing the risk of medial foot injury. It is recommended that local athletes train in the early morning or evening, pay attention to hydration and electrolyte intake, and proactively reduce training intensity and volume on hot days.

Regarding venues, urban athletes often train on riverside bike paths, PU tracks, and hard asphalt surfaces. Running on a one-directional track can cause uneven unilateral loading; alternating directions is recommended. Prolonged training on hard surfaces should be paired with appropriate footwear and gradually accumulated mileage. Taiwan’s mountainous terrain (e.g., Yangmingshan, Wuling, Beihuan) offers abundant climbing and downhill training opportunities, but long descents impose extremely high eccentric loads on joints and tendons, requiring gradual progression and enhanced eccentric tolerance.

At the event level, Taiwan’s marathon, cycling (e.g., Taiwan KOM Challenge), triathlon, and trail running events are densely packed, and the concentrated race season can tempt athletes to compress recovery for performance. A complete periodized plan should be used to connect with target races, with pre-race tapering and adequate post-race recovery. On the medical side, on-site injury identification and triage capabilities at events should be strengthened to enable early intervention and prevent minor injuries from becoming chronic conditions. Overall, combining international evidence with Taiwan’s climate, terrain, and race calendar is essential to developing prevention and rehabilitation programs truly suited to local athletes.

Common Myth-Busting

Myth 1: “You must rest completely until the pain is gone.” Complete rest may temporarily relieve symptoms, but it causes muscle loss and tissue deconditioning, actually prolonging recovery and increasing recurrence rates. The correct approach is “relative rest” combined with progressive loading under pain monitoring, allowing the tissue to receive appropriate stimulation within tolerable limits and remodel.

Myth 2: “An abnormal image means the lesion is severe and must be treated.” A large body of research shows that asymptomatic individuals also frequently have imaging abnormalities; imaging findings and symptoms do not necessarily correspond. Treatment decisions should be based primarily on clinical symptoms and functional deficits, not solely on imaging reports.

Myth 3: “Injections or anti-inflammatory medication can cure the problem.” Medications and injections are mostly symptom control and cannot replace exercise therapy that corrects load and strengthens tissue. Over-reliance on passive treatments often leads to recurrent problems.

Myth 4: “Just treat the painful area.” Overuse injuries are often the terminal manifestation of dysfunction throughout the kinetic chain. Treating only the symptom without correcting the upstream sources of load and control deficits makes recurrence likely. Comprehensive assessment and holistic intervention are the fundamental solution.

Conclusion

Accessory navicular syndrome is a typical multifactorial sports injury whose onset and recovery involve complex interactions among training load, biomechanical alignment, neuromuscular control, tissue repair capacity, and psychosocial factors. The evidence reviewed in this article consistently points to one core message: exercise therapy centered on progressive loading is the safest and most effective intervention for the vast majority of overuse injuries, while passive treatments and invasive procedures should be used judiciously and sparingly.

For athletes in Taiwan, combining international evidence with local climate, terrain, and race calendar to establish long-term habits of “load management, biomechanical strengthening, and listening to body signals” is far more critical than trying to fix problems after injury. The best treatment for sports injuries is always prevention; and once injured, following a scientific, phased rehabilitation program based on objective metrics, with gradual return to sport under professional guidance, is the true path to “returning to sport and staying injury-free.” May every sports enthusiast, on the foundation of understanding their own body, enjoy the joy of sport for the long term.

References

1. Leonard ZC & Fortin PT (2010). Foot Ankle Int
2. Kiter E et al. (2000). Foot Ankle Int
3. Knapik DM et al. (2019). Sports Health
4. Cha SM et al. (2013). J Foot Ankle Surg

Related Reading

• Metatarsal Stress Fractures in Runners: A Prospective Study on Sex Differences and Bone Density
• Conservative Treatment of Lateral Ankle Fractures: An RCT Comparing Functional Bracing vs Cast Immobilization
• Osteoarthritis and Endurance Exercise: A Scientific Clarification on Whether Running Really Harms the Knees
• Proximal Femoral Stress Reactions in Runners: A Prospective Study of Training Characteristics as Risk Factors