Ch20: Ankle Joint and Foot Flashcards
The leg (the portion of the lower extremity extending from the knee to the ankle) consists of the…
Tibia and Fibula.
What keeps the two bones together and provides a greater surface area for muscle attachment?
A strong interosseous membrane
Leg bones and interosseous membrane (anterior view).
.
The Tibia
The larger of the two bones, is the only true weight-bearing bone of the leg. Triangular in shape, the tibia’s apex (crest) is located anteriorly.
The Fibula
The long, thin fibula is set back in line with the posterior surface of the tibia. Lateral to the tibia, the fibula forms a channel, with the interosseous membrane as the floor; this permits attachment of several muscles without distorting the shape of the leg.
Medial Condyle (Tibia)
Proximal medial end
Lateral Condyle (Tibia)
Proximal lateral end
Crest (Tibia)
Anterior and most prominent of the three borders
Right leg (lateral view). Note the posterior position of the fibula.
.
Medial Malleolus (Tibia)
Enlarged distal medial surface
Head (Fibula)
Enlarged proximal end
Lateral Malleolus (Fibula)
Enlarged distal end
The bones of the foot include the…
Tarsals, metatarsals, and phalanges.
Calcaneus (Tarsal Bones)
Largest and most posterior tarsal bone
Calcaneal Tuberosity (Tarsal Bones)
Projection on the posterior inferior surface of the calcaneus
Calcaneal Tuberosity (Tarsal Bones)
Projection on the posterior inferior surface of the calcaneus
Sustentaculum Tali (Tarsal Bones)
Medial superior part projecting out from the rest of the calcaneus, supporting the medial side of the talus. Three tendons loop around this projection, changing directions from the posterior leg to the plantar foot.
Talus (Tarsal Bones)
Sitting on the calcaneus, it is the second largest tarsal
Navicular (Tarsal Bones)
On the medial side, in front of the talus and proximal to the three cuneiforms
Tuberosity of Navicular (Tarsal Bones)
Projection on the medial side of the navicular; easily seen on the medial border of the foot
Cuboid (Tarsal Bones)
On the lateral side of the foot, proximal (superior) to the fourth and fifth metatarsals and distal (inferior) to the calcaneus
Cuneiforms (Tarsal Bones)
Three in number and named the first through third, going from the medial toward the lateral side in line with the metatarsals. The first is the largest of the three.
Metatarsals
Numbered 1 through 5, starting medially. Normally, the first and fifth metatarsals are weight-bearing bones, and the second, third, and fourth are not. We tend to stand on a triangle. Weight is borne from the base of the calcaneus to the heads of the first and fifth metatarsals.
Bones of the left foot (superior, lateral, and medial views).
.
Base (Metatarsals)
Proximal end of each metatarsal
Head (Metatarsals)
Distal end of each bone
First (Metatarsals)
Thickest and shortest metatarsal; located on the medial side of the foot; articulates with the first cuneiform
Second (Metatarsals)
Longest; articulates with the second cuneiform
Third (Metatarsals)
Articulates with the third cuneiform
Fourth (Metatarsals)
Together with the fifth metatarsal, articulates with the cuboid
Fifth (Metatarsals)
Has prominent tuberosity located on the lateral side of its base
Phalanges
Of the foot have the same composition as those of the hand
The First Digit of the Foot (phalanges)
The great toe, has a proximal and distal phalanx but no middle phalanx.
The second through fifth digits of the foot (phalanges)
Aka the four lesser toes, each have a proximal, middle, and distal phalanx.
3 Parts of the foot
The Hindfoot, Midfoot, and Forefoot
The Hindfoot
Made up of the talus and calcaneus. In the gait cycle, the hindfoot is the first part of the foot that makes contact with the ground, thus influencing the function and movement of the other two parts.
The Midfoot
Made up of the navicular, the cuboid, and the three cuneiform bones. The mechanics of this part of the foot provide stability and mobility as it transmits movement from the hindfoot to the forefoot.
The Forefoot
Made up of the five metatarsals and all of the phalanges. This part of the foot adapts to the level of the ground. It is also the last part of the foot to make contact with the ground during stance phase.
Functional areas of the foot (superior view).
.
Three Main Functions of the Ankle Joint and Foot
- Acting as a shock absorber as the heel strikes the ground at the beginning of stance phase
- Adapting to the level (or unevenness) of the ground
- Providing a stable base of support from which to propel the body forward.
Plantar Flexion
Movement toward the plantar surface of the foot. (Occurs in the sagittal plane around the frontal axis)
Dorsiflexion
Occurs when the dorsal surface of the foot moves toward the anterior surface of the leg. (Occurs in the sagittal plane around the frontal axis)
Movements of the ankle joint and foot in the frontal plane around the sagittal axis are called…
Inversion and Eversion
Inversion
The raising of the medial border of the foot, turning the forefoot inward.
Eversion
The opposite motion, is the raising of the lateral border of the foot, turning the forefoot outward.
Movements of the ankle joint and foot in the transverse plane are called…
Adduction and abduction. These motions occur primarily in the forefoot and accompany inversion and eversion, respectively.
Triplanar Motion of the Ankle Joint and Foot
Better defined using the terms supination and pronation. Depending on the particular joint, and the exact orientation of its axis, some of the cardinal plane component motions will predominate more than other. In reality, the axis of motion for each joint in the ankle region is oriented at an angle. Therefore, motion at any given joint happens in an oblique plane (not in a cardinal plane)
Ankle joint and foot motions.
.
Supination
Describes a combination of plantar flexion, inversion, and adduction
Pronation
Describes a combination of dorsiflexion, eversion, and abduction
Valgus
Refers to a position in which the distal segment is situated away from the midline.
-Therefore, a calcaneal valgus is a position in which the distal (inferior) part of the calcaneus is angled away from the midline (
Varus
Refers to a position in which the distal segment is located toward the midline.
Calcaneal positions.
.
Tibiofibular Joints
Two joints, with little motion, that are not part of the true ankle joint but that play a small role in the proper function of the ankle
Superior Tibiofibular Joint
The articulation between the head of the fibula and the posterior lateral aspect of the proximal tibia. It is a plane joint that allows a relatively small amount of gliding and rotation of the fibula on the tibia. Being a synovial joint, it has a joint capsule. Ligaments reinforce the capsule, and the joint functions to dissipate the torsional stresses applied at the ankle joint.
Inferior Tibiofibular Joint
A syndesmosis (fibrous union) between the concave distal tibia and the convex distal fibula. Because it is not a synovial joint, there is no joint capsule. However, fibrous tissue separates the bones and several ligaments that hold the joint together. Much of the ankle joint’s strength depends on a strong union at this joint.
What do the ligaments holding the inferior tibiofibular joint together allow?
Slight movement to accommodate the motion of the talus.
Talocrural Joint
The true ankle joint (talocrural joint or talotibial joint) is made up of the distal tibia, which sits on the talus with the medial malleolus of the tibia fitting down around the medial aspect of the talus, and the lateral malleolus of the fibula, which fits down around the lateral aspect of the talus.
This type of joint is often described using a carpentry term: (Talocrural Joint)
Tenon and mortise joint. A mortise is a notch that is cut in a piece of wood to receive a projecting piece (tenon) shaped to fit. Therefore, the malleoli of the tibia and fibula would be the mortise, and the talus would be the tenon. This joint connects the leg and foot and is responsible for controlling the majority of foot motion relative to the leg.
The two tibiofibular joints (anterior view).
.
What kind of joint is the Ankle Joint?
The ankle is a uniaxial hinge joint consisting of an articulation of the talus with the distal end and medial malleolus of the tibia and the lateral malleolus of the fibula.
How many degrees of plantar flexion / dorsiflexion does the ankle joint allow?
The ankle joint allows approximately 30 to 50 degrees of plantar flexion and 20 degrees of dorsiflexion.
Because the axis of rotation at the ankle joint is at an angle, it is considered…
Triplanar, a term used to describe motion around an obliquely oriented axis that passes through all three planes.
During ankle dorsiflexion, the foot…
Mot only comes up but also moves out slightly (abduction).
During ankle plantar flexion, the foot moves…
Down and in (adduction).
The end feel of both dorsiflexion and plantar flexion is…
Firm and is classified as soft tissue stretch. This is due to the tension of the joint capsule, ligaments, and tendons.
Ankle joint (posterior view).
.
Triplanar axis of motion for the left ankle joint. (A) Superior view. (B) Anterior view.
.
In an open kinetic chain, with the leg fixed and the foot free to move, the angle of the joint axis causes the foot to…
Abduct during dorsiflexion and adduct during plantar flexion.
In a closed chain, with the foot fixed and the leg moving over it, the angle of the joint axis causes the leg to…
Medially rotate on the foot. During ankle plantar flexion when the foot is fixed on the ground, the leg laterally rotates on the foot. This rotation is allowed because of the slight movement that is possible at the tibiofibular joints. It is an accessory movement much like the rotation of the CMC joint of the thumb. This rotation is not possible to do in an open chain
Arthrokinematics of the Ankle Joint
The convex talus glides posteriorly on the concave tibia during ankle dorsiflexion and glides anteriorly during ankle plantar flexion.
Subtalar, or talocalcaneal, joint
Consists of the inferior surface of the talus articulating with the superior surface of the calcaneus. It is a plane synovial joint with 1 degree of freedom. The motions of inversion and eversion occur around an oblique axis.
Open Kinetic Chain (Ankle and Foot Motions)
- Leg Fixed
- Foot Moves (Ankle Dorsiflexion: Foot abducts, Ankle Plantar Flexion: Foot Adducts)
Closed Kinetic Chain (Ankle and Foot Motions)
Foot Fixed
Leg Moves: (Ankle Dorsiflexion: Leg Medially Rotates, Ankle Plantar Flexion: Leg Laterally Rotates)
Arthrokinematic motion for ankle dorsiflexion/ plantar flexion.
.
Subtalar joint (lateral view).
.
Transverse Tarsal Joint
Made up of the anterior surfaces of the talus and calcaneus articulating with the posterior surfaces of the navicular and the cuboid, respectively. Although they lie next to each other, very little movement occurs between the navicular and the cuboid. The motions of the transverse tarsal joint link the hindfoot and forefoot in inversion and eversion.
Transverse tarsal joint (superior view).
.
Motions occurring at both the subtalar and transtarsal joints.
Inversion (combination of adduction, supination, and plantar flexion) and Eversion (combination of abduction, pronation, and dorsiflexion)
What motions occur at the talocrural joint?
Plantar Flexion and Dorsiflexion
The combined motions of all these joints allow the foot to…
Assume almost any position in space. This is quite useful in allowing the foot to adapt to irregular surfaces such as those found when walking on uneven ground. For example, think about the many foot positions needed when climbing on rocks at the beach or in the mountains.
Metatarsophalangeal (MTP) Joints
Consist of the metatarsal heads articulating with the proximal phalanges. There are five joints allowing flexion, extension, hyperextension, abduction, and adduction
The first MTP joint
The most mobile. It allows approximately 45 degrees of flexion, 70 degrees of extension, and 90 degrees of hyperextension.
The second through fifth MTP joints
Allow about 40 degrees of flexion and extension and only about 45 degrees of hyperextension.
Hyperextension is very important during what phase of walking?
The toe-off phase of walking.
The point of reference for abduction and adduction of the foot joint is…
The second toe. Like the middle finger, the second toe abducts in both directions but adducts only as a return motion from abduction.
Joints of the phalanges of the foot (superior view). Note that the great toe has only two joints, whereas the four lesser toes have three.
.
Toe motions.
.
Proximal Interphalangeal (PIP) and a Distal Interphalangeal (DIP) Joint
Each of the lesser toes (2 through 5) of the foot has each these joints.
The foot has only one phalangeal joint called the…
Interphalangeal (IP) Joint
What kind of joint is the Ankle Joint
A synovial joint, has a joint capsule
Capsule of the Ankle Joint
Rather thin anteriorly and posteriorly but is reinforced by collateral ligaments on the sides. These collateral ligaments are actually groups of several ligaments.
Deltoid Ligament
The collateral ligament on the medial side is a triangular ligament whose apex is located along the tip of the medial malleolus. Its broad base spreads out to attach to the talus, navicular, and calcaneus in four parts
-Strengthens the medial side of the ankle joint, holds the calcaneus and navicular against the talus, and helps maintain the medial longitudinal arch.
Anterior Fibers of the Deltoid Ligament
Attach to the navicular (tibionavicular ligament).
Middle Fibers of the Deltoid Ligament
(Tibiocalcaneal Ligament) Descend directly to the sustentaculum tali of the calcaneus.