Ankle Flashcards
What is the true joint of the ankle and how many degrees of freedom does it have?
Tibiotarsal joint: distal joint of the lower limb
1 degree of freedom bc its a hinge joint
Joint Structure: Bones (3)
- the tibia
- fibula
- talus
what two joints make up the ankle joint
- Talocrural Joint
* Inferior tibiofibular Joint
Tibia
- distal end of the tibia is smaller than the proximal end
- flaring only medially, extends inferior to the rest of the shaft as the medial malleolus.
- The inferior surface of the shaft and the lateral surface of the medial malleolus articulate with the talus and are covered with articular cartilage.
- The interosseous border of the tibia is sharp where it gives attachment to the interosseous membrane that unites the two leg bones
- Inferiorly, the sharp border is replaced by a groove, the fibular notch, that accommodates and provides fibrous attachment to the distal end of the fibula.
Fibula
- lies posterolateral to the tibia
- Is firmly attached to it by the tibiofibular syndesmosis, which includes the in-terosseous membrane.
- The fibers of the tibiofibular syndesmosis are arranged to resist the resulting net downward pull on the fibula.
- The fibula has no function in weight-bearing
- The distal end enlarges and is prolonged laterally and inferiorly as the lateral malleolus.
Malleoli of the fibula
*form the outer walls of a rectangular socket (mortise), which is the superior component of the ankle joint, and pro-vide attachment for the ligaments that stabilize the joint
Lateral Malleoli of the fibula
is more prominent and posterior than the medial malleolus and extends approximately 1 cm more distally
Talus
Three parts
• The head carries the articulate surface of the navicular bone
• The neck, the roughened area between the body and the head, has small vascular channels
• The body features several prominent articulate surfaces: on its superior side is the trochlea tali flanked by the articulate facets for the two malleoli.
*The ankle mortise, the fork-like structure of the malleoli, holds these three articulate surfaces in a steady grip, which guarantees the stability of the ankle joint.
Talocrural Joint
This is a hinge joint formed by the distal ends of the fibula and tibula that enclose the upper surface of the talus.
It allows for both dorsiflexion (decreasing the angle between the foot and the shin) and plantarflexion (increasing the angle).
Inferior Tibiofibular joint
- This is strong joint between the lower surfaces of the tibia and fibula.
- This is supported by the inferior tibiofibular ligament.
Ligaments of the ankle: what are the names of the groups of ligaments?
Main Group *Lateral & Medial Collateral Ligaments **on either side of the joint two powerful fan-like investments which attached above at their apices to corresponding malleolus and which radiate out distally to be inserted into the tow posterior tarsal bones Accessory Groups *Anterior & Posterior Ligaments **Localized thickening of the capsule
Lateral Collateral Ligament
3 bands
- anterior talofibular
- calcaneofibular
- posterior talofibular
anterior talofibular ligament
attached: to anterior margin of fibular malleolus
run: obliquely inferiorly & anteriorly
Inserted: into talus between lateral articular facet & mouth of the sinus tarsi
calcaneofibular Ligament
Arising: from the depression in front of the apex of the lateral malleolus,
Runs: obliquely inferiorly and posteriorly
Insertion: into the lateral surface of the calcaneus
posterior talofibular Ligament
Arising: from the medial surface of the lateral malleolus behind the articular facet
Runs horizontally and inclines medially and slightly posteriorly
Insertion into the posterolateral tubercle of the talus.
Medial Collateral Ligaments
Two sets of fibers: superficial and deep( two bands)
Medial Collateral Ligaments:
Deep Anterior talotibial ligament
Runs: obliquely inferiorly and anteriorly
Attached: to the medial aspect of the neck of the calcaneus
Medial Collateral Ligaments:
Superficial
Triangular in shape, and broad, constitute the deltoid ligament.
Origin: on the medial malleolus
Run: fans out
Inserted: into a continuous line running from the tuberosity of the navicular bone, along the medial margin of the plantar calcaneonavicular ligament, to the sustentaculum tali of the calcaneus.
Inferior Tibiofibular Joint
- contains no articular cartilage
- is a syndesmosis
*The anterior ligament of the inferior tibiofibular joint, thick and pearly, runs obliquely inferiorly and laterally.
*The posterior ligament, thicker and broader, runs a long way towards the medial malleolus
The two bones are joined by the interosseous ligament between the fibular notch of the tibia and the inner surface of the fibula.
Medial Collateral Ligaments:
Deep posterior talotibial ligament
Runs: obliquely inferiorly and posteriorly
Inserted: into a deep fossa on the medial surface of the calcaneus
*its most posterior fibres are attached to the posteromedial tubercle
Muscular Structures:
Compartments of the Leg
Anterior, Lateral & posterior compartments
Muscular Structures:
Anterior Compartment of the Leg:
Extensor (dorsiflexor):
general
located anterior to the interosseous membrane, between the lateral surface of the shaft of the tibia and the medial surface of the shaft of the fibula, and anterior to the intermuscular septum that connects them.
Muscular Structures:
Anterior Compartment of the Leg:
Extensor (dorsiflexor):
Tibialis Anterior
Origin: the lateral condyle and superior half of lateral surface of tibia and interosseous membrane
Insertion: medial and inferior surfaces of medial cuneiform and base of 1st metatarsal.
Function: Dorsiflexes ankle and inverts foot.
Muscular Structures:
Anterior Compartment of the Leg:
Extensor (dorsiflexor):
Extensor Digitorum Longus
Origin: the lateral condyle of tibia and superior three quarters of medial surface of fibula and interosseous membrane
Insertion: middle and distal phalanges of lateral four digits
Function: Extends lateral four digits and dorsiflexes ankle
Muscular Structures:
Anterior Compartment of the Leg:
Extensor (dorsiflexor):
Extensor Hallucis Longus
Origin: Middle part of anterior surface of fibula and interosseous membrane
Insertion: dorsal aspect o base of distal phalanx of great tow(hallux)
Function: Extends big tow and dorsiflexes ankle
Muscular Structures:
Lateral Compartment of the Leg:
Evertor
General
- Smallest compartment
- surrounded by lateral surface of fibula, anterior and posterior intramuscular septa and deep fascia of the leg.
*ends inferiorly at the superior fibular retinaculum, which spans between the distal tip of the fibula and the calcaneus
Muscular Structures:
Lateral Compartment of the Leg:
Evertor:
Fibularis longus
Origin: the head and superior two thirds of lateral surface of fibula
Insertion: the base of 1st metatarsal and medial cuneiform.
Function: Everts foot and weakly plantarflexes ankle
Muscular Structures:
Lateral Compartment of the Leg:
Evertor:
Fibularis brevis
Origin: the inferior two thirds of lateral surface of fibula
Insertion: the dorsal surface of tuberosity on lateral side of base of 5th metatarsal.
Function:Everts foot and weakly plantarflexes ankle
Muscular Structures:
Posterior Compartment of the Leg:
Flexor
General
- Plantarflexor compartment
- Largest compartment
- Deep & Superficial
Muscular Structures: Posterior Compartment of the Leg: Flexor: Superficial: Gastrocnemius
Lateral head: lateral aspect of lateral condyle of femur
Medial head: Origin: popliteal surface of femur; superior to medial condyle.
Insertion: Posterior surface of calcaneus via calcaneal tendon.
Function: Plantarflexes ankle when knee is extended; raises heel during walking; flexes leg at knee joint.
Muscular Structures: Posterior Compartment of the Leg: Flexor: Superficial: Soleus
Origin: the posterior aspect of head and superior quarter of posterior surface of fibula; soleal line and middle third of medial border of tibia; and tendinous arch extending between the bony attachments
Insertion: Posterior surface of calcaneus via calcaneal tendon.
Function:Plantarflexes ankle independent of position of knee; steadies leg on foot.
Muscular Structures: Posterior Compartment of the Leg: Flexor: Superficial: Plantaris
Origin: the Inferior end of the lateral supracondylar line of the femur; oblique popliteal ligament
Insertion: Posterior sur-face of calcaneus via calcaneal tendon.
Function: Weakly assists gastrocnemius in plantarflexing ankle.
Muscular Structures: Posterior Compartment of the Leg: Flexor: Deep: Popliteus
Origin: Lateral surface of lateral condyle of femur and lateral meniscus
Insertion: Posterior surface of tibia, superior to soleal line.
Function: Weakly flexes knee and unlocks it by rotating femur 5° on fixed tibia; medially rotates tibia of un-planted limb.
Muscular Structures: Posterior Compartment of the Leg: Flexor: Deep: Flexor hallucis Longus
Origin: the Inferior two thirds of posterior surface of fibula; inferior part of interosseous membrane
Insertion: base of dis-tal phalanx of the big toe (hallux).
Function: Flexes great toe at all joints; weakly plantarflexes ankle; supports medial longitu-dinal arch of foot.
Muscular Structures: Posterior Compartment of the Leg: Flexor: Deep: Flexor digitorum Longus
Origin: the medial part of posterior surface of tibia inferior to soleal line; by a broad tendon to fibula
Insertion:the bases of distal phalanges of lateral four digits.
Function: Flexes lateral four digits; plantarflexes ankle; supports longitudinal arches of foot.
Muscular Structures: Posterior Compartment of the Leg: Flexor: Deep: Tibialis Posterior
Origin: the Interosseous membrane; posterior surface of tibia inferior
Insertion: soleal line; posterior surface of fibula to the tuberosity of navicular, cuneiform, cuboid, and sustentaculum tali of calcaneus; bases of 2nd, 3rd, and 4th metatar-sals.
Function: Plantarflexes ankle; inverts foot.
How many degrees of freedom does the ankle have as a whole?
3
allows the foot to take up any position in space and adapt to irregularities of the ground.
The transverse axis (X) passes through the two malleoli and corresponds to the axis of the ankle proper. It lies almost wholly in the frontal plane and controls the movements of flexion and extension of the foot, which occur in a sagittal plane.
The long axis of the leg Y is vertical and controls the movements of adduction and abduction of the foot, which take place in a transverse plane.
The long axis of the foot Z is horizontal and lies in a sagittal plane. It controls the movements of the sole of the foot and allows it to face inferiorly, laterally or medially. These movements can be called pronation and supination respectively.
Flexion
- the movement, which approximates the dorsum of the foot and the anterior surface of the leg.
- It is also called dorsiflexion.
- Its range is from 20°to 30°
• checked by the following factors
Bony factors:
• During extreme flexion the upper surface of the neck of the talus comes into contact with the anterior margin of the tibial surface.
Capsular and ligamentous factors:
• The posterior part of the capsule is stretched as well as the posterior fibres of the collateral ligaments.
Muscular factor:
• The resistance offered by the tonically active soleus and gastrocnemius muscles usually limits flexion before the other two factors.
Extension
- the movement of the dorsum of the foot away from the anterior surface of the leg so that the foot tends to fall into line with the leg
- It is also called plantar flexion
- Its range is from 30° to 50°
• checked by the following factors:
Bony factors:
• The posterior tubercles of the talus, especially the posterolateral tubercle, strike the posterior margin of the tibial surface.
Capsular and ligamentous factors:
• the anterior part of the capsule is stretched as well as the anterior fibres of the collateral ligaments
Muscular factor:
• The resistance offered by the tonically active flexor muscles is the first limiting factor.
The anteroposterior stability of the ankle
- depend upon the effect of gravity, which keeps the talus pressed against the distal surface of the tibia
- the anterior and posterior margins of the tibial surface form bony spurs which prevent the talar pulley from escaping anteriorly or posteriorly.
- The collateral ligaments are passively responsible for the coaptation of the surfaces and are assisted, by the muscles provided the joint is intact.
The transverse stability of the ankle
Being a joint with a single degree of freedom, the ankle cannot, by virtue of its very structure, exhibit movements around its two other axes in space.
This stability depends upon the tight interlocking of
its surfaces: in fact it is analogous to a tenon-and-mortise joint, with the talar tenon being tightly fitted into the tibio-fibular mortise.
