Lower Leg Anatomy & Biomechanics

Abnormal Pronation

• The session covers posterior leg compartment musculature
• The session aims to understand pronation and the difference between pronation and abnormal pronation
• The session involves understanding the function of the talocrural joint and awareness of the ankle ligaments

Posterior Group Leg Muscles (Superficial)

• Gastrocnemius origin is the medial and lateral condyles of the femur's posterior surface
• Gastrocnemius insertion is the posterior calcaneus (Achilles)
• Gastrocnemius action is plantarflexion of the ankle and flexion of the knee
• Soleus origin is the upper two-thirds of the posterior surface of the tibia and fibula
• Soleus insertion is the posterior calcaneus (Achilles)
• Soleus action is plantarflexion of the ankle when the knee is past 30 degrees of flexion
• Plantaris origin is the lateral supracondylar ridge of the femur
• Plantaris insertion is the posterior calcaneus (via or separate to Achilles)
• Plantaris action is a weak ankle plantarflexion and knee flexion

Posterior Group Leg Muscles (Deep)

• Tibialis Posterior origin is the upper one-third of the tibia and fibula, and interosseous membrane
• Tibialis Posterior insertion is the navicular tuberosity, cuboid, cuneiforms, and bases of metatarsals 2-4
• Tibialis Posterior action is adducting and inverting the foot with assisting ankle plantarflexion
• Flexor Digitorum Longus origin is the central one-third of the the posterior tibia.
• Flexor Digitorum Longus insertion is plantar base of distal phalanges toes 2-5
• Flexor Digitorum Longus action is flexion of toes 2-5, with ankle plantarflexion, and weak inversion.
• Flexor Hallucis Longus origin is distal two-thirds posterior shaft of fibula
• Flexor Hallucis Longus insertion is the plantar base of the distal phalanx of the hallux
• Flexor Hallucis Longus action is flexion of the hallux, ankle plantarflexion, and weak inversion

Pronation

• Pronation involves motion of foot articulations that allows it to be more prone to the support surface
• Pronation increases the ground contact surface area of the foot
• Pronation is essential for plantigrade bipedal gait
• Pronation allows initial compliance and later passive foot stiffening

Over-Pronation

• Over-pronation/hyper-pronation/excessive-pronation has been philosophically but not quantitatively defined
• Attempts have been made to semi-quantitatively define hyper pronation
• A range of motion within the foot is induced that makes the foot more prone to the support surface
• The motion is greater than that required for an individual to adjust to morphology dealing with forces placed on the musculoskeletal system by kinetic and kinematic events within gait or another given action

Pronation Assessment

• Aspects of pronation assessment include concepts of reliability and validity
• Aspects of pronation assessment include Subtalar Neutral Position
• Aspects of pronation assessment includes the Arch Index
• Aspects of pronation assessment includes Foot print indices

Subtalar joint neural position

• To identify the pathology troubling the patient (diagnosis).
• To identify abnormal situations from normal.
• The key examinations used to make inferences about dynamic foot function and to determine orthotic prescription are unreliable
• Root et al approach, The 8 Biomechanical Criteria For Normalcy.,RCSP and NCSP have very poor intertester reliability with 1st ray motion poor to moderate.
• Accuracy of measurements is not achievable and it is not possible to identify normal from abnormal
• "Using these examinations to differentiate normal from pathological foot function would not appear to be valid clinical practice”

Arch Height Index

• Dorsal height taken at 50% length of entire foot and divide by the length between the posterior heel to the 1st metatarsal head to derive index.
• Can use total foot length unless toe deformities are present
• AHI taken sitting (10% bw) to standing to reflect weightbearing (50% bw) and arch stiffness with the difference measures representing the stiffness
• Longitudinal arch angle correlates with angle
• Curvilinear relationship noted between body mass% and arch deformation.

Problems With Arch Height

• Good inter and intra tester reliability.
• It's a static measure
• There is no correlation between arch height and dynamic maximum eversion of rearfoot
• There is no correlation between arch index to disabling foot pain, balance, gait function, or falls
• Classifying foot type to height to length ratio shows no relationship

Foot Print Indices

• Uses footprints or pressure mats printouts to map out contact areas
• Relationship poor to fair is defined a low arch = more medial midfoot, hallux pressure, lower medial forefoot
• It is important to determine if there is a link to pathology and ‘normal’ arch needs to be assessed

Longitudinal Arch Angle.

• Uses Two lines between most prominent point medial 1st metatarsal and medial malleolus with apex at navicular tuberosity
• 120-150° ‘normal' but disagreement exists
• Highly predictive of foot posture at midstance
• There is inter-rater reliability issues with unknown validity to pathology or treatment

Arch Measures Conclusions

• Dynamic arch angle correlations can exist
• No correlation between arch height and dynamic maximum rearfoot eversion can exist
• No correlation between arch height and foot pain in older individuals can exist
• No correlation with arch height and balance, function or falls can exist

Navicular Drop

• Navicular Drop is the height of navicular tuberosity in talar head congruency position to relaxed stance position
• Strong association with radiographic arch height on stance at RCSP
• Associations with gait function & balance tests, and walking speed.
• There is No significant correlation with foot pains or falls

Navicular Drift

• Navicular Drift adds in transverse plane motion as well as sagittal
• All the validity problems of navicular drop exists

Foot Posture Index

• Multi-foot segment & multiplanar
• Simple and quick to use
• With training: good inter-tester reliability

Foot Posture Index (FPI-6)

• This predicts only 41% of dynamic foot position variation.
• Asymptomatic groups had larger feet which have lower FPI
• Taller and heavier people higher FPI (57% in normal group)
• More mobile feet have a higher FPI
• There is no association with disabling foot pain
• There is no associations between fallers and non-fallers.

Using Foot Posture Index (FPI-6)

• Use as an assessment tool of rehabilitation/treatment success
• Use for Evaluation of foot orthosis position
• If changes in foot posture after 60 mins of running at 3.3 ms causes increased scores if foot posture, use with extreme caution!

Supination test

• Finger pressure is poor reliability when correlation with mechanical device
• Accuracy of the mechanical device unknown
• There is, no association with pain or function

STJ axis and magnitude of pronation

• Depending on the joint axis of the subtalar joint, a greater or lower magnitude of force will be required to indite pronatory or supinatory moments,
• The force in question must be placed to the appropriate location

Talocrurual Articulation

• Ankle joint.
• Identify how these deficits might affect Gait.
• Design a management plan for someone with deficits in these joints.

Review Of Anatomy

• The ankle joint is a hinged synovial joint formed by the articulation of the talus, tibia,and fibula bones which creates an ankle mortise.
• The articular facet of the lateral malleolus (bony prominence on the lower fibula) forms the lateral border of the ankle joint
• The superior portion of the ankle joint forms from the inferior articular surface of the tibia and the superior margin of the talus.
• The talus articulates inferiorly with the calcaneus and anteriorly with the navicular.

Ankle Anatomy

• The upper surface, called the trochlear surface, is a bit cylindrical and allows for dorsiflexion and plantarflexion of the ankle with abduction and adduction capabilities
• The talus is wider anteriorly and more narrow posteriorly, with the medial and lateral malleoli (mortise and tenon) ensuring stability
• Dorsiflexion is the most stable position for the ankle.

Ankle Joint Ligaments

• Medial Collateral (Deltoid) Ligament
• Anterior Talofibular Ligament
• Calcaneofibular Ligament
• Posterior Talofibular Ligament

Joint Capsule

• The articular capsule surrounds the joints, and attaches, above, to the borders of the articular surfaces of the tibia
• The capsule joint anteriorlyis a thin and fibrous layer, with thin fibers posteriorly which run transversely, blending with the transverse ligament
• Laterally the capsule is thickened and attaches to the hollow on the medial surface of the lateral malleolus
• The synovial membrane extends superiorly between Tibia & Fibula as far as the Interosseous Tibiofibular Ligament

Talocrural Joint and Assessing ROM

• ATFL - Most commonly injured (85)

Talocrural Joint and Assessing ROM Cont...

• The Talar Tilt test is used
• During test patient is supine with foot unsupported grasping the calcaneum with one hand and tibia with other hand
• Ankle is plantarflexed and inverted
• The CFL / Deltoid test is performed the same but the ankle is inverted and everted with 50% Sensitivity and 88% Specificity

Anterior Drawer Assessment

• Assesses the ATFL
• Patient is in supine position.
• Grasp calcaneum with one hand and tibia with other hand – Ankle Plantarflexed 15 degrees
• Patient pulls firmly anterior on the calcaneum whilst maintaining tibia position.
• Sensitivity: 71% (Specificity: 33%)

Posterior Drawer Assessment

• Assesses the PTFL
• Patient position is in Supine with the Knee Flexed
• The practitioner Grasp the calcaneum with one hand and tibia with other hand, and places Ankle Plantarflexed 15 degrees
• Pressure is maintained firmly anterior on the calcaneum whilst maintaining tibia position
• A positive suclus sign sub lateral malleolus to prove test true

Kliegers external rotation test

• Assists in identifying tibiofibular syndesmotic injury
• The term High Ankle sprain refers to an injury solely involving the tibiofibular syndesmosis and/or inferior tibiofibular ligaments
• Grasp calcaneum and talus in one hand, Ankle maximally dorsiflexed and Hold tibia stable with other hand while Externally rotate foot relative to leg
• +ve if reproduction of symptoms in anterior lateral aspect of ankle with 20% Sensitivity and 85% Specificity

The Squeeze Test

• Syndesmosis Injury is being tested with Fibula compressed against tibia at the midpoint of the calf where +ve test is distal pain at tibio-fibular joint.

The Cotton Test

• Syndesmosis injury is being tested
• Stabilise the tibia with one hand, and The other hand grasps the calcaneus and talus and test foot
• Talis is rocked into inversion and eversion in the ankle mortice
• +ve when a characteristic click is felt with reciprocation of pain

Assessment Effects Of Gait

• Limitation on ankle Dorsaflexion / Plantarflexion will inhibit forward progression of the body over the ankle
• The reported normal available range for dorsiflexion varies in the literature between 0-16.50[1] and 0-250[2] changing weight bearing
• The normal Plantarflexion range has been reported 0°-50°
• Early heel lift, bouncy gait are typical effects
• Externally is typically rotated.

Ankle Injury Impacts

• This can cause (CAI) from Syndesmosis Injury or Ankle sprain – Inversion
• Uncompensated from rearfoot varus Loss of proprioception
• High re injury rate can occur due to loss of proprioception
• The most commonly is injured is the structure (20% of sports injuries)

Treatments and Techniques

• • Orthoses may need heel raises which also include stretching gastroc and posterior muscle groups

Treatments for joint ROM can include

• Rocker bottom shoes and Eccentric exercises
• With Mobilization of the ankle
• Post injury soft tissue work on ligaments can increase ROM

Summary of Positions

• Forefoot Supinatus: means a fully or partially flexible inverted forefoot to the rearfoot.
• Forefoot Varus: means a rigid inverted forefoot because of osseous disposition
• Forefoot Valgus: means a rigid or flexitble version due to midtarsal joints
• Neutral Forefoot: means A forefoot that exists in the same frontal plane level as the rearfoot
• Rearfoot Varus: means a calcaneum that is inverted to the plane in STJ neutral
• Rearfoot Valgus: means a calcaneum that is everted to the plane in STJ neutral

Final Positions

• Neutral Rearfoot: A calcaneum that is perpendicular to the plane in STJ neutral.
• Uncompensated: Means no change between NCSP and RCSP positions
• Partially Compensated: means Some reduction in deformity between NCSP and RCSP but deformity remains.
• Compensated: means the Deformity is reduced when moving from NCSP to RCSP.
• Pes Cavus: Means a High Arch Foot
• Calcaneo-: Dorsiflexion is the primary deformity seen and present
• Equino / Equinus: Means Plantarflexion is the primary deformity
• Pes Planus: Means Low Arch Foot