Structure and Function of the Ankle and Foot Chapter 11 Structure and Function of the Ankle and Foot Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Ankle and Foot Terminology Plantar aspect of foot refers to sole or bottom of foot Dorsal aspect refers to top or superior portion of foot Rearfoot, midfoot, and forefoot are commonly used clinical terms that indicate specific areas of feet Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Overview of Gait Cycle Gait cycle describes events that occur (while walking) within two successive heel contacts of same leg Each gait cycle is divided into a stance phase (events that occur when foot is in contact with ground) and a swing phase (events that occur when foot is swinging through air) Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Swing Phase and Stance Phase Stance phase elements (1) heel contact; (2) foot flat; (3) mid stance; (4) heel off; (5) toe off Swing phase elements (1) early swing; (2) mid swing; (3) late swing Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Osteology: Distal Tibia and Fibula Medial malleolus Medial projection of bone from the distal tibia Lateral malleolus Projects laterally from distal fibula Both malleoli serve as proximal attachments for collateral ligaments of ankle Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Osteology: Distal Tibia and Fibula – cont’d Fibular notch Concave portion of distal tibia that articulates with fibula, forming distal tibiofibular joint Distal tibiofibular joint Firm articulation allows little gliding between tibia and fibula Serves as stable socket that accepts superior portion of talus—forming talocrural (ankle) joint Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Osteology: Foot Bones Three sets of bones Tarsals Metatarsals Phalanges Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Tarsal Bones Tarsal bones include: Talus, calcaneus, navicular, cuboid Medial, intermediate, and lateral cuneiforms Three cuneiforms form transverse arch of foot Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Rearfoot Talus Trochlea: dome-shaped superior portion Three facets on plantar aspect for articulation with calcaneus Head: articulates with navicular Calcaneus Calcaneal tuberosity: attachment of Achilles tendon Three facets on superior aspect for articulation with talus Sustentaculum talus: medial projection of bone that serves as shelf to support talus Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Midfoot Navicular Navicular tuberosity: prominent medial projection of bone; site of distal attachment for spring ligament and tibialis posterior muscle Cuneiforms Forms medial half of transverse arch of foot Cuboid Forms lateral half of transverse arch of foot Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Forefoot Metatarsals—all 5 consist of: Concave base (proximal aspect) Shaft Convex head (distal aspect)  Phalanges—all 14 consist of: Concave base Convex head Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Kinematics of Ankle and Foot Fundamental movements occur within a plane perpendicular to three classic axes of rotation: medial-lateral, anterior-posterior, and vertical Many joints produce an oblique movement best described with the applied terms of pronation or supination Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Fundamental Movements: Dorsiflexion and Plantar Flexion Dorsiflexion and plantar flexion occur in sagittal plane about a medial-lateral axis of rotation Dorsiflexion describes bringing dorsal part (top) of foot toward anterior aspect of tibia Plantar flexion describes moving dorsal part of foot away from anterior aspect of tibia Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Fundamental Movements: Inversion and Eversion Inversion and eversion occur in frontal plane about an anterior-posterior axis of rotation Inversion turns a point anywhere on plantar aspect of foot toward midline Eversion turns a point on plantar aspect of foot laterally, or away from, midline Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Fundamental Movements: Abduction and Adduction These motions occur in horizontal plane about a vertical axis of rotation Adduction describes horizontal plane rotation of foot that moves toward midline Abduction describes horizontal plane rotation of foot that rotates away from midline Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Fundamental Movements: Pronation and Supination Pronation is a combined movement of eversion, abduction, and dorsiflexion of any region of ankle and foot Supination is a combined movement of inversion, adduction, and plantar flexion of any region of ankle and foot Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Proximal Joints: Talocrural Joint Ankle joint, created by the articulation between trochlea (dome) of talus and concavity formed by distal tibia and fibula This concave part of joint is often referred to as “mortise” because of its resemblance to a mortise joint used by carpenters Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Kinematics: Talocrural Joint One degree of freedom permitting ankle dorsiflexion plantar flexion, sagittal plane motions important to walking and squatting Muscles coursing anterior to medial-lateral axis of rotation perform dorsiflexion; muscles that course posterior perform plantar flexion Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Arthrokinematics: Talocrural Joint With foot free, an open-chain dorsiflexion and plantar flexion occur as convex trochlea rolls and slides in opposite directions within concave mortise With foot fixed, concavity formed by mortise rolls and slides in same direction over convex dome of talus Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Supporting Structures: Talocrural Joint Interosseous membrane Binds tibia to fibula Provides stability to distal tibiofibular and talocrural joints Anterior and posterior tibiofibial ligaments Bind distal tibiofibular joint, improving stability of the mortise Deltoid ligament Limits eversion Lateral collateral ligament Limits inversion Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Positions of Talocrural Joint Ankle is most stable during maximal dorsiflexion when most collateral ligaments and all plantar flexor muscles are stretched Least stable position of talocrural joint is full plantar flexion when most collateral ligaments and all plantar flexor muscles are slackened Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Proximal Joints: Subtalar Joint Articulation between facets on inferior surface of talus and matching facets on superior surface of calcaneus Designed to allow frontal and horizontal plane motions between foot and lower leg, motions essential for adapting to uneven ground surfaces or “cutting” laterally or medially Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Kinematics: Subtalar Joint Allow combined motions of inversion/adduction and eversion/abduction of foot Side-to-side motions are inversion and eversion Rotary (horizontal plane) motions are adduction and abduction During all subtalar motions, trochlea is normally well stabilized within mortis shape of talocrural joint Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Subtalar Joint Motion at subtalar joint allows independent movement between calcaneus and talus, a path that cuts through both frontal and horizontal planes While walking, this motion occurs either when calcaneus is free, or held fixed under body’s weight While in stance phase of walking, leg and talus move “as one” over fixed calcaneus Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Transverse Tarsal Joint Features Consists of talonavicular joint and calcaneocuboid joint Allows midfoot to move independently of rearfoot Permits most pure form of pronation and supination: pronation has nearly equal elements of eversion, abduction, and dorsiflexion; supination has nearly equal elements of inversion, adduction, and plantar flexion Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Medial Longitudinal Arch of Foot Load-bearing and shock absorbing foot structure Active muscle forces are generally not required to support arch while standing (an exception being someone with pes planus) Arch normally lowers, and rearfoot everts slightly to maintain forces at tolerable levels Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Medial Longitudinal Arch: Primary Passive Supporting Structures Plantar fascia Spring ligament Many plantar ligaments Integrity of talonavicular joint Deltoid ligament Shapes of tarsal bones Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Medial Longitudinal Arch: Primary Active Supporting Structures Tibialis posterior Peroneus longus Intrinsic muscles of plantar aspect of foot Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Distal Joints of Foot Include tarsometatarsal, metatarsophalangeal, and interphalangeal joints All three of these joints play an important role in walking Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Distal Joints: Tarsometatarsal Joints Articulation of metatarsal bases with distal surfaces of three cuneiforms and cuboid Serve as base joints for rays of foot Relatively rigid, except for first, allowing dorsiflexion and plantar flexion, coupled with inversion and eversion Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Distal Joints: Metatarsophalangeal Joints Formed between convex head of metatarsals and shallow concavity of proximal phalanges Allow similar motions to analogous metacarpophalangeal joints in hand: extension (dorsiflexion), flexion (plantar flexion), and abduction and adduction Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Distal Joints: Interphalangeal Joints Each toe has a proximal and distal interphalangeal joint, except great toe with only one interphalangeal joint Motion is limited primarily to flexion and extension Extension is typically limited to 0-degree or neutral position of joint Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Muscle and Joint Interaction Intrinsic muscles have both proximal and distal attachments within foot Extrinsic muscles have proximal attachments within lower leg or distal femur, and distal attachments within foot Muscles provide static control, dynamic thrust, and shock absorption to distal lower extremity Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Innervation to Extrinsic Muscles of Ankle and Foot Extrinsic muscles of foot are arranged into anterior, lateral, and posterior compartments Each compartment is innervated by tibial or common peroneal nerve, arising from sciatic nerve Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Innervation to Extrinsic Muscles of Ankle and Foot – cont’d Tibial nerve continues distally through lower leg Common peroneal nerve courses laterally, wraps around fibular head, and splits into superficial peroneal and deep peroneal nerves Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Innervation to Intrinsic Muscles of Foot Tibial nerve bifurcates into medial and lateral plantar nerves These nerves innervate all intrinsic muscles of foot, except for extensor digitorum brevis (innervated by deep branch of peroneal nerve) Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Anterior Compartment Muscles Tibialis anterior, extensor digitorum longus, extensor hallucis longus, and peroneus tertius Originate on anterior and lateral aspects of proximal tibia, adjacent fibula, and interosseous membrane All four muscles are innervated by deep peroneal nerve and perform dorsiflexion as one of their primary actions Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Foot Drop Foot “drops” into plantar flexion as leg is advanced during swing phase of gait In order to prevent foot from dragging, often a “high-stepping” gait is performed that appears like stepping over an imaginary obstacle   Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Foot Slap If dorsiflexors are unable to generate sufficient eccentric activation between heel contact and foot flat, forefoot quickly drops to ground Referred to as foot slap due to sound that occurs as sole of foot hits floor Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Shin Splints Condition that may affect muscles attached to medial and posterior sides of tibia Often involves dorsiflexor muscles If dorsiflexors are untrained or mechanics of foot and ankle are faulty, these muscles may become inflamed through overuse Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Shin Splints – cont’d Excessive pronation of foot during running or walking often exacerbates or contributes to shin splints For this reason, clinicians often recommend orthotics to help support foot and provide inflamed dorsiflexor muscles much relief Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Lateral Compartment Muscles: Peroneus Longus Proximal attachment Lateral condyle of tibia; head and proximal 2/3 of lateral surface of fibula Distal attachment Lateral surface of medial cuneiform and base of first metatarsal Actions Eversion Plantar flexion Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Lateral Compartment Muscles: Peroneus Brevis Proximal attachment Distal 2/3 of lateral surface of fibula Distal attachment Styloid process of the fifth metatarsal  Actions Plantar flexion Eversion Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Lateral Compartment Muscles Provide an important element of muscular stability to lateral aspect of ankle and foot With weakness of peroneal muscles, foot is more likely to “flip” strongly into inversion, possibly resulting in lateral ankle sprain Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Posterior Compartment Muscles Superficial group Gastrocnemius, soleus, and plantaris Deep group Tibialis posterior, flexor digitorum longus, and flexor hallucis longus All muscles are innervated by tibial nerve and perform a combination of plantar flexion and inversion (supination) Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Soleus versus Gastrocnemius Soleus is composed of primarily slow-twitch muscle fibers best equipped for standing or controlling “postural sway” Gastrocnemius, on the other hand, is composed of more fast-twitch fibers best equipped for sprinting and jumping   Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Raising Up on Tiptoes Ease of standing up on tiptoes is largely due to mechanical advantage of plantar flexors during this action Plantar flexors function as a second-class lever system, providing a mechanical system that favors strength over speed and range of motion Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Functional Considerations: Supporting Medial Longitudinal Arch Non-contractile supporting structures of medial longitudinal arch may overstretch, leading to excessive pronation In response, deep group muscles of posterior compartment help support medial longitudinal arch Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Intrinsic Foot Muscles Intrinsic muscles that originate and insert within foot are largely responsible for actions of toes As a group these muscles stabilize foot during push-off phase of walking or running Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Dorsum of Foot Extensor digitorum brevis Proximal attachment dorsal-lateral aspect of calcaneus, just proximal to calcaneocuboid joint Distal attachment Through four separate tendons that blend with extrinsic extensor tendons coursing to digits 1-4 Actions Extension of first four toes Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Plantar Aspect of Foot First layer Flexor digitorum brevis, abductor hallucis, and abductor digiti minimi Second layer Quadratus plantae and four lumbricals Third layer Adductor hallucis, flexor hallucis brevis, and flexor digiti minimi Fourth layer Dorsal and plantar interossei Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc. Summary Structure of ankle and foot designed to absorb impact of weight bearing and adapt to shape of ground Dysfunctions of hip, knee, or even back may be associated with problems originating at ankle or foot Copyright © 2014, 2009 by Mosby, an imprint of Elsevier Inc.