Courtney Conley is an internationally renowned foot and gait specialist. In this episode, Courtney delves into the intricate world of foot anatomy and functionality. She explores the complexities of the foot, discussing its anatomy, common injuries, and the importance of understanding its structure in preventing issues.
The Complexity and Importance of the Foot
- The human foot is a complex structure, comprising 26 bones and 33 joints.
- It is described as a "superpower" of the human species, being our first interface with the ground and crucial for bipedal movement.
- The foot contains numerous cutaneous receptors, muscle spindles, and joint proprioceptors that communicate with the vestibular system, enabling upright posture.
- A powerful analogy likens feet to a race car's tires and suspension; without healthy feet, the "engine" (the rest of the body) cannot effectively transfer power or absorb force, leading to issues throughout the body. This highlights the need to focus strength training below the knee, rather than just above.
Key Anatomical Structures and Their Functions
- The foot is divided into three parts: the rearfoot, midfoot, and forefoot.
- Rearfoot:
- Calcaneus (Heel Bone): Designed for shock absorption, with a thin cortical outer layer and a spongy inner layer, akin to a bouncing rubber ball. It also features a fat pad that is two times more effective at shock absorption than sorbane (a synthetic material used in orthotics).
- Talus: Sits under the tibia and fibula; unique for having zero muscle attachment, relying solely on ligaments. Ligament damage (e.g., from repeated ankle sprains) can lead to talus migration and pain. Neurological input is crucial here, as stretched or torn nerves (e.g., superficial peroneal nerve) can lead to loss of sensation, making recurrent sprains more likely.
- Midfoot:
- Navicular: The highest point of the medial arch, with the posterior tibialis muscle inserting on its bottom. Stress fractures here are typically caused by tensile strain due to inability to control foot pronation and rotation.
- Sustentaculum Tali: A medial lip off the calcaneus that fully ossifies by age seven; its development can be affected by footwear, influencing arch development and stability. A study found children who wore shoes had a higher prevalence of flat feet (9%) compared to those who didn't (3%), suggesting sensory input from going barefoot helps in arch elevation.
- Forefoot:
- Consists of metatarsals and phalanges. It experiences eight times body weight with propulsion during walking, making it a common site for injuries.
- Sesamoids: Two small bones under the big toe, completely embedded within tendons, similar to the patella.
Muscles of the Foot and Lower Leg
- Foot muscles are categorised as intrinsic (originating and ending in the foot) or extrinsic (originating outside the foot). The foot has four layers of intrinsic muscles.
- Intrinsic Muscles:
- Abductor Hallucis: Straightens the big toe (moves it away from the midline); a slow-twitch muscle important for balance and sustained posture.
- Adductor Hallucis: Pulls the big toe towards the middle. Imbalances between abductor and adductor hallucis due to narrow shoes can lead to bunions.
- Flexor Digitorum Brevis: Runs from the heel to the toes, parallel to the plantar fascia; responsible for decelerating toe extension and is a major predictor of plantar fasciitis when weak.
- Extrinsic Muscles:
- Posterior Tibialis: A major medial foot stabilizer and inverter, decelerates pronation, and shows constant activation throughout the stance phase of gait. Its 45-degree rotational attachment makes it crucial for energy storage and propulsion.
- Peroneals (Brevis and Longus): On the lateral side of the ankle; powerful everters of the foot. Peroneus Longus wraps under the foot to the medial aspect and anchors the big toe for stable push-off. Dysfunction can lead to instability and pain.
- Tibialis Anterior and Toe Extensors: Located on the front of the lower leg; responsible for dorsiflexion (pulling toes back). They are crucial for ground clearance during swing phase to prevent tripping and for eccentric control at heel strike to decelerate the foot and prevent "foot slap". Weakness can lead to shin splints.
- Soleus: The largest muscle of the lower leg, composed of more slow-twitch (Type I) fibers, making it a Workhorse for endurance. It's a powerhouse for creating force at the forefoot and is very important in the prevention of ACL injuries by resisting tibial progression. A metric for its strength is performing a single-leg seated calf raise with 1.5 times body weight.
- Gastrocnemius: Works with the soleus to form the Achilles tendon; less endurance than soleus but generates more force.
Foot Mechanics and Gait
- The foot needs to both pronate (flatten and widen) for shock absorption and supinate (lift and narrow) for propulsion. Pronation should not be demonised but rather controlled.
- The Tie Bar Mechanism is a "free" mechanism of stability: when the forefoot splays during midfoot loading, it triggers receptors in the deep transverse metatarsal ligament, which tensions the plantar fascia, creating horizontal and vertical stability for push-off. This mechanism is compromised by narrow footwear.
- Effective gait requires adequate and controlled range of motion.
Common Foot Injuries and Pathologies
- Fall Risk: Toe strength is the single biggest predictor of falls in the elderly, with a 35% decline in strength between young adulthood and older age. Loss of sensory input (75% decreased sensitivity in receptors from age 50 to 85) also significantly increases fall risk.
- Plantar Fasciitis/Fasciopathy: Common heel pain, often chronic, linked to weakness in muscles like flexor digitorum brevis. Treatment should focus on strengthening the foot and loading the tissue, rather than just resting or relying on long-term orthotics.
- Metatarsalgia and Stress Fractures: Common in the forefoot, especially the 2nd and 3rd metatarsals. Stress fractures can be due to compressive loading (e.g., calcaneus, 5th metatarsal) or tensile strain (e.g., navicular). Treatment differs based on the cause, with tensile-strain fractures requiring strength rehabilitation.
- Bunions (Hallux Valgus): A transverse instability where the metatarsal shifts outwards, often caused by muscle imbalances (shortened adductor, lengthened abductor hallucis) from narrow footwear. Surgical repair often fails to address the underlying muscular weakness.
- Hammer Toes: Toes (typically 2-5) "hammer" the ground due to muscle imbalances, specifically weak short flexors and overactive long flexors on the bottom of the foot, and overactive short extensors with relaxed long extensors on top. This is also linked to general neglect of foot strength and footwear choices.
- Hallux Limitus/Rigidus: A restriction of motion at the big toe. Functional Hallux Limitus is due to muscular weakness and instability, causing jamming and irritation. It requires 40-45 degrees of range for efficient walking. If untreated, it can progress to Hallux Rigidus, involving significant arthritic changes and potential fusion of the joint. Early intervention with strengthening can prevent progression.
- Achilles Tendinopathy: Can be mid-tendon or insertional (at the calcaneus), with insertional being more challenging due to the breakdown on the front of the tendon. Tendons need load to heal and strengthen; rest alone is not sufficient. Managing discomfort (e.g., 5/10 pain scale) is part of the rehabilitation process.
- Peroneal and Posterior Tibialis Tendinopathy: Also common, requiring movement and load for healing.
Diagnosis and Assessment Tools
- Toe Dynamometer: Measures toe strength; individuals should be able to produce 10% of their body weight through the big toe and 7-8% through toes 2-5, without lifting the heel or hammering toes.
- Anterior Fall Envelope Test: Measures the distance one can lean forward from a wall (umbilicus to wall) without falling, relying on toe strength; 4.5 inches or more is desirable.
- Ankle Dorsiflexion: 10-15 degrees is needed for walking, but 35 degrees is an ideal functional range. Lack of dorsiflexion can lead to compensations like early heel rise, knee hyperextension, or forward bending at the hips.
- Seated Single-Leg Calf Raise: Assesses Solus strength, aiming for 1.5 times body weight for six repetitions.
- Vibration Tool (256 frequency): Used to test sensory perception in the foot, important for balance and fall prevention.
- Clinical history and physical exam are primary; imaging (e.g., diagnostic ultrasound for stress fractures) is used for specific issues, but MRI provides limited valuable information for most tendonopathies.
Treatment and Rehabilitation Principles
- Strength Training: Cornerstone of treatment for most foot pathologies, including plantar fasciitis, bunions, and hallux limitus. "If you don't use it, you will lose it" applies to the foot's capacity to handle load.
- Loading Tendons: Tendons require load (mechano transduction) to heal and strengthen, not just rest.
- Isometrics: Act as "pain meds" by decreasing cortical inhibition, allowing the brain to "let off the brake" and facilitating movement even in the presence of pain or injury.
- Proximal Stability: Foot issues are rarely isolated; assessing and training core, hip (glute Max for internal rotation control, glute Med for stability), and overall body stability is crucial.
- Movement Control: Emphasises controlling range of motion, rather than just having it. The concept of "no bad posture, only bad control" suggests the ability to move in and out of various positions is key to foot health.
- Early Intervention: Addressing foot issues in children (e.g., through appropriate footwear) can prevent long-term structural deformities like bunions and hammer toes.
- Addressing Neurological Inhibition: Sometimes, the body's inability to achieve a certain range of motion is due to a neurological "braking" mechanism (e.g., for stability) rather than a physical restriction.
Footwear Recommendations
- For Kids: Encourage frequent barefoot activity on various surfaces. Choose shoes with a wide toe box and flexible, thin soles to allow natural foot development.
- For Adults:
- Wide Toe Box: Non-negotiable; allows toes to splay, activating the tie bar mechanism and improving balance. An easy test is to place your foot on the shoe's factory insert; if your forefoot is wider than the insert, the shoe is too narrow.
- Zero Drop: Heel and toe should be on the same plane, mimicking natural foot posture. Any elevation in the heel is considered a "high heel". A slight heel-to-toe drop (e.g., 8mm) can be tolerated with appropriate foot strength and mobility.
- Thin, Flexible Sole (Minimal Stack Height): Allows the foot to feel the ground, which cues the body to land lighter and activates receptors important for shock absorption. Thicker, cushioned soles (high stack height) can speed up pronation, requiring stronger foot control.
- Performance Shoes: (e.g., super running shoes with carbon plates and high stack heights) can offer advantages but should be "earned" by building foundational foot strength and used only for specific activities, not daily training, to avoid injuries.
- Toe Spacers: Recommended for daily use to encourage toe splay, especially for conditions like bunions or neuromas. Start gradually (e.g., 5 minutes barefoot daily) to allow the feet to adapt.
- Fashionable Footwear: Acknowledged that people will wear them, but a higher burden of responsibility for foot strengthening and mobility work is required to compensate.
Running Mechanics and Footwear
- Running in minimalist shoes requires preparing the foot and calf with adequate capacity.
- The key to efficient running is striking the foot as close to the center of mass as possible, rather than over-striding. This often leads to a midfoot or forefoot strike, shifting load from knees, hips, and back to the foot and calf.
Chapters
0:00:00 Intro
0:01:11 Why Courtney chose to specialize in the foot
0:04:12 The vital role of foot strength, function, and health in human movement and well-being
0:08:25 Anatomy of the rear foot and midfoot
0:19:10 The development of flat feet, the impact of footwear, and the benefits of going barefoot
0:23:20 Anatomy of the forefoot, common injuries, and why most injuries occur in the forefoot
0:31:00 Foot musculature and its role in maintaining foot stability and preventing deformities like bunions and hammer toes
0:41:00 The intrinsic musculature of the foot, plantar fasciitis, footwear, & more
0:54:41 Plantar fasciitis: diagnosis, causes, and treatment
1:03:45 Posterior leg muscles: strength assessment methods, role in ACL injuries, & more
1:09:27 Lateral and medial muscles: ankle stability, arch support, big toe stabilization, and exercises to strengthen and prevent injuries
1:13:56 Importance of strength of lower leg muscles for gait and preventing shin splints, stress injuries, & more
1:19:21 Tendinopathies and other common pathologies related to the anterior and lateral compartments of the foot
1:26:55 The importance of midfoot integrity and ankle dorsiflexion and a discussion of gait alterations
1:34:57 Proximal stability and its implications for posture and movement patterns
1:41:23 The age-related decline in foot sensation and strength
1:45:49 Common toe injuries, treatment, and how to prevent further progression of the injury
1:57:33 Preventing falls & managing arthritis with proactive foot care & exercises
2:06:20 Footwear: advice for picking shoes that promote foot health
2:19:05 Footwear for runners
2:23:39 The importance of prioritizing footwear that promotes natural foot movement & strength while considering individual comfort & foot health needs