Ankle & foot joint

Question 1

What type of joint is the ankle?

Answer 1

• The ankle joint, or talocrural joint, is a synovial joint of the modified hinge variety.
• The axis of rotation is not fixed but changes between the extremes of plantarflexion and dorsiflexion.
• The articulating surfaces are covered with hyaline cartilage.
• The weight-bearing surfaces are the upper trochlear facet of the talus and the inferior facet of the tibia.
• Stabilising surfaces are those of the medial and lateral malleoli, which grip the sides of the talus.

Question 2

Describe the capsule of the ankle.

Answer 2

• The joint is enclosed in a capsule lined with synovial membrane.
• The capsule is attached to the articular margins of all three bones except the anterior part of the talus, where it is fixed some distance in front of the articular margin, on the neck of the bone.
• Posteriorly the capsule, on its way up to the tibia, is attached also to the posterior tibiofibular ligament.
• The synovial membrane is attached to the articular margin of the talus and clothes the intracapsular part of the neck. Elsewhere it is attached to all articular margins and lines the inside of the capsule.

Question 3

Outline the medial ligament of the ankle.

Answer 3

• Strong medial and lateral ligaments strengthen the joint.
• The deltoid ligament, on the medial side, is in two layers.
• The deep part is a narrow band extending from the tibial malleolus to the side of the talus.
• The superficial part is triangular, like a delta. It fans downwards from the borders of the tibial malleolus and its lower margin has a continuous attachment from the medial tubercle of the talus along the edge of the sustentaculum tali and spring ligament to the tuberosity of the navicular.

Question 4

Outline the lateral ligaments of the ankle.

Answer 4

• On the lateral side there are three separate bands, radiating from the lateral malleolus, which are collectively commonly called the lateral ligament. * Anterior and posterior bands pass to the talus, the intermediate band to the calcaneus.
• The anterior talofibular ligament joins the anterior border of the lateral malleolus to the neck of the talus.
• The calcaneofibular ligament extends from the tip of the malleolus down and back to the lateral surface of the calcaneus.
• The posterior talofibular ligament lies horizontally between the malleolar fossa of the fibula and the lateral tubercle of the talus.
• Above it lies the posterior tibiofibular ligament, whose lower part (also called the inferior transverse ligament) is covered by hyaline cartilage and articulates with the talus.
• In plantarflexion these two ligaments lie edge to edge, but in dorsiflexion they diverge like the blades of an opening pair of scissors.

Question 5

Describe plantar/dorsiflexion of the ankle.

Answer 5

• From the upright position, with the foot at right angles to the leg, active plantar flexion of about 20˚is produced by gastrocnemius and soleus, assisted by the long flexor tendons and the long and short peronei.
• Active dorsiflexion of about 10˚is produced by tibialis anterior, the long toe extensors and peroneus tertius.
• The degree of passive movements possible is approximately double the above.

Question 6

Describe the blood and nerve supply of the ankle.

Answer 6

• The blood supply of the capsule and ligaments is derived from anterior and posterior tibial arteries and the peroneal artery.
• The nerve supply is by the deep peroneal and tibial nerves.

Question 7

Outline the main tarsal joints.

Answer 7

• The most important joints in the tarsus are those between the talus, calcaneus and navicular and between the calcaneus and cuboid.
• On the undersurface of the talus there are two separate joints.
• At the back is the talocalcanean joint, where the upper surface of the calcaneus articulates with the undersurface of the talus.
• In front of this is a more complicated joint, with part of the undersurface of the head of the talus articulating with the upper surface of the sustentaculum tali and body of the calcaneus and the spring ligament, and the front of the head of the talus articulating with the navicular. The whole joint with its single synovial cavity is called talocalcaneonavicular.

Question 8

Describe the talocalcaneonavicular joint.

Answer 8

• Synovial joint of the ball and socket variety.
• The ball is the head of the talus and the socket comprises the navicular and calcaneus and the spring ligament.
• The posterior surface of the navicular has an articular surface which is concave reciprocally with the anterior convexity of the head of the talus.
• The anterior end of the upper surface of the calcaneus has a concave facet, and the sustentaculum tali a similar one for articulation with the inferior convexity of the head of the talus.
• Between these navicular and calcanean surfaces the head of the talus articulates with the fibrocartilaginous upper surface of the spring ligament.
• All these structures are enclosed in a single capsule.

Question 9

Describe the talocalcanean joint.

Answer 9

• Lies behind the talocalcaneonavicular joint. * It is a synovial joint between the concave facet on the undersurface of the talus and the convex facet on the upper surface of the calcaneus.

Question 10

Describe the calcaneocuboid joint.

Answer 10

• Separate synovial joint between the front of the calcaneus and the back of the cuboid.
• This and the talonavicular part of the talocalcaneonavicular joint form what is usually called the midtarsal joint.
• The calcaneocuboid joint is surrounded by a capsule, thickened above and below. * The long and short plantar ligaments are accessory ligaments on its plantar surface.
• Simple gliding movement takes place at this joint during inversion and eversion of the foot.

Question 11

What are the main tarsal joint ligaments.

Answer 11

• Short and long plantar ligaments.
• Spring ligament.
• Bifurcate ligament.

Question 12

Describe the plantar ligaments.

Answer 12

• The short plantar ligament (properly called the plantar calcaneocuboid) is a thick bundle which fills in the adjacent hollows in front of the anterior tubercle of the calcaneus and behind the posterior ridge of the cuboid.
• It is covered over by the long plantar ligament.
• The long plantar ligament is attached to the plantar surface of the calcaneus anterior to its tuberosity, and to the anterior tubercle of that bone.
• From here it extends forwards to cover the short plantar ligament, and its deeper fibres are attached to the posterior ridge of the cuboid.
• Its superficial fibres bridge the groove of the cuboid, making a fibrous roof over the peroneus longus tendon, and are attached to the anterior ridge of the cuboid and extend forwards to the bases of the central three metatarsal bones.
• It is covered by flexor accessorius, and its posterior part is visible in the gap between the medial fleshy and lateral tendinous heads of that muscle.
• Various other smaller but stronger interosseous plantar ligaments unite adjacent bones and help to support the arches of the foot.

Question 13

Describe the spring ligament.

Answer 13

• The plantar calcaneonavicular (spring) ligament is a very strong band that connects the anterior edge of the sustentaculum tali to the plantar surface of the navicular.
• Its upper surface articulates with the head of the talus, and bears a fibrocartilaginous facet for this purpose.
• Its lower fibres extend well under the sustentaculum tali and lie almost transversely across the foot.
• Like ligaments in general, it consists of collagenous tissue and, despite its common name ‘spring ligament’, it is not elastic.

Question 14

Describe the bifurcate ligament.

Answer 14

• The bifurcate ligament arises from the upper surface of the calcaneus, under cover of the extensor digitorum brevis muscle at the front of the tarsal sinus. * From this origin two limbs diverge from each other.
• The medial limb is attached to the navicular and the lateral limb is attached to the cuboid.

Question 15

Outline the tarsal sinus.

Answer 15

• The tarsal sinus lies obliquely between the talocalcaneonavicular joint and the talocalcanean joint. * It is a cylindrical canal that opens anteriorly at its lateral end like the broad end of a funnel.
• The sinus is occupied by a strong, flat bilaminar interosseous talocalcanean ligament.
• The central portion of each bony gutter is perforated by vascular foramina.
• At the lateral end of the sinus is the cervical ligament between the neck of the talus and the upper surface of the calcaneus.

Question 16

Describe inversion/eversion of the foot.

Answer 16

• Inversion and eversion of the foot occur at the subtalar and midtarsal joints, more movement occurring at the former joint.
• Adduction and supination of the forefoot accompany inversion. Abduction and pronation of the forefoot accompany eversion.
• The range of inversion is increased in plantarflexion, and the fully inverted foot is also plantarflexed.
• The more restricted movement of eversion is linked in an allied manner with dorsiflexion.
• The movement of inversion (raising the medial border of the foot) is produced by any muscle that is attached to the medial side of the foot. Tibialis anterior and tibialis posterior are responsible, assisted by extensor and flexor hallucis longus on occasion.
• The movement of eversion (raising the lateral border of the foot) is produced by any muscle that is attached to, or pulls upwards upon, the lateral side of the foot. Peroneus longus, brevis, and tertius are responsible.
• All the muscles producing inversion and eversion are attached to the fore part of the foot, anterior to the midtarsal joint.
• The calcaneus and cuboid are firmly connected by the long and short plantar ligaments, which limit the range of mobility at the midtarsal joint; when they and the spring ligament are taut they transmit the rotatory force to the calcaneus.
• This bone then rotates (i.e. inverts or everts) under the talus, which is firmly wedged against the tibia between the malleoli and cannot therefore be inverted or everted.