The deep flexors of the lower leg — the posterior tibial tendon (PTT), flexor digitorum longus (FDL), and flexor hallucis longus (FHL) — are essential yet often underrated in discussions of leg and foot function. They are key players in our balance, gait, and ability to engage in activities that require foot dexterity.
In this article, we'll uncover the roles of the deep flexors from an anatomical and biomechanical standpoint using the Motion Specific Release (MSR) perspective. We'll explore the PTT's role in maintaining the foot's arch, the FDL's function in curling the smaller toes, and the FHL's importance in the push-off phase of walking with a focus on the big toe.
Article Index:
Deep Flexors Anatomy & Biomechanics
The PTT, FDL, and FHL are the deep flexor muscles of the lower leg, crucial for the intricate movements of the foot and ankle. These muscles are not as visible as the gastrocnemius and soleus, but their function is vital for the foot's stability, support, and fine motor actions.
Posterior Tibial Tendon (PTT)
The PTT is key for maintaining the arch of the foot and supporting its structure. It is a central force in controlling the inward movement of the foot (inversion) and the downward movement (plantarflexion).
Origin and Insertion:
It originates from the posterior tibia, interosseous membrane, and fibula, and inserts into the bones of the foot, primarily the navicular and secondarily the cuneiforms and cuboid bones.
Innervation:
The tibial nerve innervates the PTT, with nerve roots from L4 to S1.
Biomechanical Role:
The PTT provides stability during the contact phase of walking and is crucial for the push-off phase. It supports the foot's arch and plays a role in the absorption and redistribution of forces during gait.
Flexor Digitorum Longus (FDL)
The FDL flexes the lateral four toes and assists with foot stabilization during the stance phase of gait.
Origin and Insertion:
It arises from the mid-posterior tibia and inserts into the distal phalanges of the four lesser toes.
Innervation:
Also innervated by the tibial nerve, with nerve roots from L5 to S2.
Biomechanical Role:
The FDL's primary function is toe flexion, but it also supports the arch and controls midfoot and forefoot movements during walking and running.
Flexor Hallucis Longus (FHL)
The FHL is the powerhouse for flexing the big toe, an action that's crucial for powerful push-offs, such as when sprinting or jumping.
Origin and Insertion:
It originates on the lower posterior fibula and interosseous membrane, and inserts into the base of the distal phalanx of the big toe.
Innervation:
Innervated by the tibial nerve, the FHL has nerve roots from L5 to S2.
Biomechanical Role:
The FHL is vital for balance and propulsion, aiding in the final thrust during the toe-off phase of gait.
Motion Specific Release (MSR) Treatment
For the deep flexors of the calf, namely the PTT, FDL, and FHL, Motion Specific Release (MSR) procedures are tailored to address the unique biomechanical roles and anatomical structures of these muscles.
Initial Setup:
Patient Position: The patient starts in a prone position to relax the gastrocnemius and soleus muscles, then shifts to a kneeling position to access the deep flexors effectively.
Practitioner Stance: The practitioner adjusts their stance to facilitate deep manual access to the PTT, FDL, and FHL.
Basic Technique:
Treatment Hand:Â The practitioner uses their fingers or the heel of the hand to apply targeted pressure to the deep flexors, navigating deeper beyond the gastrocnemius and soleus.
Support Hand: The other hand supports the foot or the leg, facilitating specific movements to engage the deep flexors.
Synchronization: Careful coordination is needed to maintain the correct depth and motion.
Pressure:Â The pressure is carefully increased to engage the deeper muscles without causing undue discomfort.
Focus Area:Â The practitioner focuses on areas of restriction within the deep flexors, maintaining pressure and manipulating the foot to achieve a release.
Advanced Maneuver:
For each muscle, specific maneuvers are applied:
For the PTT, emphasis is placed on supporting the arch and facilitating inversion and plantarflexion movements.
The FDL is engaged by flexing the lateral four toes, supporting the arch, and performing circumduction to address the entire length of the muscle.
The FHL requires a focus on flexing the big toe and plantarflexing the ankle, with attention given to its passage beneath the Achilles tendon.
Fiber Composition & Orientation:
Understanding the fiber composition of these muscles is crucial for MSR techniques. While the deep flexors primarily consist of slow-twitch fibers suited for sustained postural support, they also contain fast-twitch fibers necessary for quick, reflexive movements. The practitioner's movements should align with the fiber orientation to maximize effectiveness.
MSR Demonstration Video:
The video features Dr. Abelson showcasing MSR procedures tailored for the PTT, FDL, and FHL.
Best Practices:
Time Factor: Sufficient time should be allocated for the MSR session, allowing for a methodical approach to releasing these deep muscles.
Circumduction Benefits:Â Circumduction and multi-directional movements facilitate myofascial release and enhance proprioceptive feedback and neuromuscular coordination.
Kinetic Chains: The interconnectedness of the PTT, FDL, and FHL within the lower limb kinetic chain is considered, recognizing their impact on both local and systemic musculoskeletal health.
Precautions:
Prioritize patient safety by considering contraindications and ensuring informed consent.
Avoid exacerbating any existing conditions by using gentle, informed techniques.
Be aware of the patient's comfort and response to pressure throughout the MSR session.
Functional Kinetic Chains
Understanding the kinetic chains associated with the PTT, FDL, and FHL is essential for a holistic view of musculoskeletal health and for applying effective treatments such as Motion Specific Release (MSR). This perspective helps us appreciate:
Direct Myofascial Connections
The PTT, FDL, and FHL form a myofascial continuum that transmits forces and facilitates complex foot and ankle movements. Disruptions within this continuum can have widespread effects, impacting gait and stability.
Medial Ankle Ligaments: The PTT, particularly, is connected to the medial ankle ligaments, influencing the stability and movement of the inner foot.
Long Plantar Ligament: Works with the FDL and FHL to maintain the longitudinal arch and enables force transmission along the sole of the foot.
Interosseous Membrane:Â Shares force and proprioceptive information between the deep flexors, critical for nuanced foot movements.
Synergists
These muscles complement the actions of the deep flexors, contributing to the dynamic stability and movement of the foot.
Anterior Tibialis: Works with the PTT to control foot inversion and support the medial arch.
Peroneals: Balance the inversion action of the PTT by providing eversion, contributing to lateral stability.
Stabilizers
These muscles are the structural framework that ensures the integrity and efficiency of foot movements.
Quadratus Plantae: Helps modulate the force of the FDL during toe flexion, ensuring precise movements.
Lumbricals: Act in concert with the FHL to stabilize the toes during gait and when standing.
Antagonists
Muscles that oppose the actions of the PTT, FDL, and FHL are crucial for controlled and balanced foot mechanics.
Dorsiflexors: Oppose the plantarflexion action of these deep flexors, crucial for movements like walking up stairs or releasing the foot from a tiptoed position.
Extensor Digitorum Longus: Counterbalances the toe flexion action of the FDL, important for lifting the toes during the swing phase of gait.
This integrated view of the PTT, FDL, and FHL within the kinetic chains provides invaluable insights into foot mechanics. It is fundamental for developing targeted treatment and rehabilitation protocols that address the interconnectivity of the lower limb's musculoskeletal system.
Exercises
Flexibility/Mobility Exercises
Stretching the Calf Muscles
This video provides stretches for both your calf muscles the gastrocnemius, soleus, and the deep flexors. Only minor changes in technique can make a huge difference in increasing your calf flexibility.
Myofascial Release
Calf Muscle Release - Lacrosse Ball & Foam Roller
The gastrocnemius with the soleus, your calf muscles are the main plantar flexors of the ankle joint. In addition, this also helps to release the deep flexors.
Strengthening Exercises
Eccentric Calf Raises
The Eccentric Calf Raise is an effective method for enhancing calf strength while minimizing the risk of further injuries. Dynamic calf pulsations serve as an optimal exercise for augmenting sports performance and power. This is an advanced exercise; thus, ensure that you can effortlessly execute standard Eccentric Calf Raises & Pulsations before attempting this variation.
Balance/Proprioception
Improve Your Balance
Exercises for Beginners: Balancing exercises are crucial components in both Rehabilitation and Sports Performance training. These exercises should not be overlooked, as they can bolster one's capacity to stabilize the body during functional movements. By incorporating straightforward balance exercises into a progressive training program, you can enhance balance and avert injuries.
Precautions:
Exercises involving the calves and deep flexors, especially plyometrics, should be approached with caution to avoid overstraining these muscles. Individuals with prior calf injuries or those who are inexperienced with plyometric exercises should consult a healthcare provider before beginning such routines. Proper warm-up and progression are essential to prevent injury and facilitate muscle adaptation.
Conclusion
This article has detailed the critical yet often overlooked roles of the lower leg's deep flexors: the posterior tibial tendon (PTT), flexor digitorum longus (FDL), and flexor hallucis longus (FHL). Understanding their anatomy, biomechanics, and involvement in kinetic chains provides a comprehensive view necessary for effective diagnosis and treatment.
The Motion Specific Release (MSR) techniques demonstrated here offer a pathway to enhancing the function and resilience of these deep flexors. Integrating these practices into treatment and exercise regimens can significantly improve foot stability, gait, and overall performance.
DR. BRIAN ABELSON, DC. - The Author
Dr. Abelson's approach to musculoskeletal health care reflects a deep commitment to evidence-based practices and continuous learning. In his work at Kinetic Health in Calgary, Alberta, he focuses on integrating the latest research with a compassionate understanding of each patient's unique needs. As the Motion Specific Release (MSR) Treatment Systems developer, he views his role as both a practitioner and an educator, dedicated to sharing knowledge and techniques that can benefit the wider healthcare community. His ongoing efforts in teaching and practice aim to contribute positively to the field of musculoskeletal health, with a constant emphasis on patient-centered care and the collective advancement of treatment methods.
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ReferencesÂ
Abelson, B., Abelson, K., & Mylonas, E. (2018, February). A Practitioner's Guide to Motion Specific Release, Functional, Successful, Easy to Implement Techniques for Musculoskeletal Injuries (1st edition). Rowan Tree Books.
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Hammer, W. I. (2007). Functional Soft-Tissue Examination and Treatment by Manual Methods (3rd ed.). Jones and Bartlett Publishers.
 Järvinen, T. A. H., Järvinen, T. L. N., Kääriäinen, M., Kalimo, H., & Järvinen, M. (2007). Muscle Injuries: Biology and Treatment. The American Journal of Sports Medicine, 33(5), 745–764.
Liebenson, C. (2006). Rehabilitation of the Spine: A Practitioner's Manual (2nd ed.). Lippincott Williams & Wilkins.
Myers, T. W. (2001). Anatomy Trains: Myofascial Meridians for Manual and Movement Therapists. Churchill Livingstone.
Neumann, D. A. (2010). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation (2nd ed.). Mosby Elsevier.
Page, P., Frank, C. C., & Lardner, R. (2010). Assessment and Treatment of Muscle Imbalance: The Janda Approach. Human Kinetics.
Schleip, R., & Müller, D. G. (2013). Training Principles for Fascial Connective Tissues: Scientific Foundation and Suggested Practical Applications. Journal of Bodywork and Movement Therapies, 17(1), 103–115.
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