1. Tibialis Posterior → Adult Acquired Flatfoot / Progressive Collapsing Foot Deformity (AAFD / PCFD)
Anatomy & Normal Function
Courses posterior to medial malleolus; inserts primarily on the navicular and medial midfoot.
Major dynamic stabilizer of the medial longitudinal arch.
Controls subtalar inversion, supports talonavicular joint, and contributes to midfoot locking mechanism during push-off.
Pathoanatomy
Tendon degeneration, elongation, or rupture → progressive loss of medial support.
Secondary failure of static stabilizers: spring ligament, deltoid ligament, talonavicular capsule, interosseous ligaments.
Leads to:
Hindfoot valgus and peritalar subluxation
Medial arch collapse
Talus plantarflexion/adduction and forefoot abduction (“too many toes”)
Imaging
Weight-bearing AP Foot
Talonavicular uncoverage (%) – often increased
Talus–1st Metatarsal Angle (AP Meary’s) – often increased
Talo–calcaneal angle (Kite angle) – often increased
Weight-bearing Lateral Foot
Meary’s Angle (Talo–1st MT): plantar apex shift
Calcaneal Pitch: often decreased
Talus declination angle: increased
Gait & Kinetic Chain Effects
Excessive pronation during stance; talar internal rotation with increased subtalar eversion.
Ground reaction force shifts laterally; tibial internal rotation increases.
May contribute to valgus knee moments and patellofemoral maltracking symptoms.
Clinical Clues
Medial ankle pain and tenderness along the posterior tibial tendon.
“Too many toes sign” on posterior inspection.
Single heel-rise test: weakness or inability to invert heel into varus.
Management Overview
Stage I (Early / flexible stages)
Immobilization for painful tenosynovitis, orthotics (medial arch support), stretching and strengthening.
Stage II (flexible deformity)
Goals: restore medial column alignment and replace tendon function.
Common combinations:
FDL transfer to navicular
Medializing calcaneal osteotomy
± lateral column lengthening
± spring ligament reconstruction
± gastrocnemius recession/Achilles lengthening
Stage III–IV (rigid / arthritic deformity)
Fusion-based procedures (double or triple arthrodesis).
Clinical Message: Early identification and treatment slow progression and reduce surgical complexity.
2. Peroneus Longus → Cavus / Cavovarus Foot
Anatomy & Normal Function
Originates from lateral fibula; passes posterior to lateral malleolus to insert on 1st metatarsal base and medial cuneiform.
Functions:
Plantarflexes the 1st ray
Provides lateral column stability
Supports forefoot lever during push-off
Pathoanatomy
In neuromuscular disorders (e.g., Charcot-Marie-Tooth), peroneus longus remains relatively strong, while tibialis anterior and peroneus brevis weaken.
Result:
1st ray plantarflexion → medial column rigidity and high arch
Progressive hindfoot varus and lateral column overload
Even subtle cavus may present with recurrent ankle instability and lateral foot pain.
Clinical Evaluation
Coleman block test:
If hindfoot varus corrects with lateral column support → deformity is forefoot-driven.
Assess 1st ray mobility and peroneal–tibialis anterior muscle balance.
Consider neuromuscular exam when appropriate.
Imaging
o Lateral Foot
§ Meary’s Angle → increased apex dorsally
§ Calcaneal Pitch → elevated
§ Coleman relationship indirectly inferred
· AP Foot
· Forefoot adduction / supination assessment
· Medial/lateral column comparative morphology
Gait & Kinetic Consequences
Plantarflexed 1st ray makes the foot rigid → decreased shock absorption.
Increased lateral loading → lateral column stress fractures, sinus tarsi pain.
Elevated ankle inversion moments → recurrent sprains and chronic instability.
Proximal chain effect: varus knee tendencies and compensatory hip/lumbar adaptations.
Management Overview
Nonoperative
Orthoses with lateral posting; gastrosoleus stretching; proprioceptive training.
Surgical Principles
Goal: plantigrade, balanced foot.
When PL “overdrive” is present:
Peroneus longus → brevis transfer to reduce 1st ray plantarflexion and improve eversion strength.
Structural corrections as needed:
1st metatarsal dorsiflexion osteotomy
Calcaneal lateralizing osteotomy
Middle foot osteotomies for fixed deformity
Clinical Message: Addressing peroneus longus imbalance is critical; isolated bony correction without tendon balancing risks recurrence.
3. Gastrosoleus Complex → Equinus Deformity
Anatomy & Function
Gastrocnemius crosses knee and ankle; soleus acts at ankle only.
Unite as Achilles tendon; primary plantar flexor.
Controls tibial advancement eccentrically in stance and generate power during push-off.
Classification and Key Test
Silfverskiöld test
Dorsiflexion improves with knee flexion → isolated gastrocnemius tightness.
Dorsiflexion restricted even with knee flexion → combined gastrosoleus/Achilles contracture.
Pathoanatomy & Associated Problems
Chronic equinus limits dorsiflexion; compensations include:
Midfoot pronation and medial arch collapse (planovalgus)
Increased forefoot loading → metatarsalgia, plantar fasciitis, ulcers (especially in diabetes)
In neuromuscular disease → equinovarus combinations possible
Gait Effects
Early heel rise, toe-walking pattern, inefficient gait.
Proximal compensations: knee hyperextension, increased patellofemoral load, altered hip and lumbar mechanics.
Frequently worsens AAFD (Adult Acquired Flatfoot) progression; must be addressed in reconstruction planning.
Management Overview
Nonoperative: stretching programs, splinting, footwear modification.
Surgical
Isolated gastrocnemius contracture → gastrocnemius recession (e.g., Strayer).
Combined contracture → Achilles tendon lengthening.
Avoid over-lengthening to prevent calcaneus gait and loss of push-off strength.
4. Kinetic Chain, Gait Cycle, and Load Transfer
Gait Overview
One cycle: heel strike → subsequent heel strike of same limb.
Stance ≈ 60% (weight bearing), swing ≈ 40%.
Foot transitions sequentially through shock absorption → stabilization → propulsion.
Role of the Foot in the Kinetic Chain
Terminal interface of the lower limb kinetic chain.
Modulates ground reaction forces through tibia, knee, hip, and pelvis.
Subtalar motion influences tibial rotation and knee frontal/transverse plane mechanics.
Deformity-Specific Chain Effects
Adult Acquired Flatfoot / Progressive Collapsing Foot Deformity (AAFD / PCFD)
Excess pronation, hindfoot valgus → tibial internal rotation, valgus knee moment increase, reduced push-off efficiency.
Cavus / Cavovarus
Rigid medial column → lateral overload, stress injury risk, recurrent instability.
Equinus
Early heel-off, forefoot overload, compensatory midfoot pronation; mixed cavus–planovalgus patterns may appear across phases.
Practical Clinical & Surgical Principles
Always evaluate the entire kinetic chain, not only the foot.
In AAFD surgery:
Treat associated gastrosoleus tightness to prevent under-correction or recurrence.
In cavovarus reconstruction:
Assess and correct peroneus longus dominance; tendon balancing is essential.
In equinus management:
Standardize Silfverskiöld testing; incorrect Achilles lengthening leads to major functional compromise.
References
1- Polichetti C, Borruto MI, Lauriero F, et al. Adult Acquired Flatfoot Deformity: A Narrative Review about Imaging Findings. Diagnostics (Basel). 2023;13(2):225. Published 2023 Jan 7. doi:10.3390/diagnostics13020225
2- Myerson MS, Thordarson DB, Johnson JE, et al. Classification and Nomenclature: Progressive Collapsing Foot Deformity. Foot Ankle Int. 2020;41(10):1271-1276. doi:10.1177/1071100720950722
3- Ross MH, Smith M, Plinsinga ML, Vicenzino B. Self-reported social and activity restrictions accompany local impairments in posterior tibial tendon dysfunction: a systematic review. J Foot Ankle Res. 2018;11:49. Published 2018 Aug 30. doi:10.1186/s13047-018-0292-z
4- Maynou C, Szymanski C, Thiounn A. The adult cavus foot. EFORT Open Rev. 2017;2(5):221-229. Published 2017 May 11. doi:10.1302/2058-5241.2.160077
5- Henry JK, Shakked R, Ellis SJ. Adult-Acquired Flatfoot Deformity. Foot Ankle Orthop. 2019;4(1):2473011418820847. Published 2019 Jan 16. doi:10.1177/2473011418820847