Session 5a - Bones And Joints Of The Distal Lower Limb

Question 1

What bones does the leg contain?

Answer 1

The leg contains two bones, the tibia and fibula. They are connected via two joints and a strong interosseous membrane. The distal ends of both bones articulate with the talus at the ankle joint.

Question 2

What is the tibia like?

Answer 2

The tibia is a thick and strong bone. Its expanded proximal end articulates with the femur to form the knee joint. Its distal end is tapered and articulates with the talus and fibula.

Question 3

What does the tibia form?

Answer 3

The proximal part of the tibia forms medial and lateral tibial condyles. The superior surfaces of the condyles, the medial and lateral tibial plateaus, are flattened. They articulate with the femoral condyles to form the knee joint. The intercondylar tubercles are prominent ridges located between the tibial plateaus.

Question 4

Where is the tibial tuberosity?

Answer 4

The tibial tuberosity projects from the upper anterior surface of the tibia and is easily palpable through the skin. The patellar ligament inserts here.

Question 5

What surrounds the tibial tuberosity?

Answer 5

Distal to this, the sharp anterior border of the shaft of the tibia is easily palpable through the skin. Posteriorly, the soleal line is an oblique ridge on the posterior surface of the tibia. Distally, the medial malleolus projects medially from the distal end of the bone and forms part of the ‘socket’ for the talus.

Question 6

What is the fibula like?

Answer 6

The fibula is a slender bone. Its proximal end does not contribute to the knee joint.

Question 7

What is the fibula composed of?

Answer 7

The proximal part of the fibula is expanded and forms the head, which is palpable through the skin and the neck is located just distal to the head. The common fibular nerve runs close to the bone here.

Question 8

What surrounds the fibula?

Answer 8

The shaft of the fibula is slender and is an attachment site for muscles. Distally, the lateral malleolus projects from the distal end of the bone and forms part of the ‘socket’ for the talus.

Question 9

How is the foot adapted for its function?

Answer 9

The human foot carries the weight of the body and is adapted for bipedal gait. The small joints of the foot allow it to deform and absorb shock when walking over uneven ground. Part of the sole of the foot does not make contact with the ground when we stand but is raised by the longitudinal and transverse arches of the foot. These are formed by the arrangement of the bones of the foot and allow shock absorption. The arches are supported by ligaments and tendons in the foot.

Question 10

What is the foot composed of?

Answer 10

The tarsal bones which comprise the following:
- the talus
- calcaneus (heel bone)
- navicular
- cuboid
- three cuneiforms (medial, intermediate, and lateral)

Question 11

What forms the hindfoot and midfoot?

Answer 11

The talus articulates with the tibia and fibula at the ankle joint. The talus and calcaneus are referred to as the hindfoot. The navicular, cuboid and cuneiforms comprise the midfoot.

Question 12

What do the names of the tarsal bones mean?

Answer 12

The name ‘calcaneus’ is derived from the Latin word for ‘chalk’, owing to its dense white appearance and structure. Navicular means ‘boat-shaped’ as its curved shape resembles the hull of a small boat and cuneiform means ‘wedge-shaped’ as, when the cuneiforms bones are viewed in the coronal plane, they are all wedge shaped.

Question 13

What forms the forefoot?

Answer 13

The metatarsals and phalanges comprise the forefoot.

Question 14

What is the arrangement of the foot?

Answer 14

The metatarsals are numbered 1 – 5 from the medial (great toe) side to the lateral (little toe) side. Just like in the hand, the bones of the digits (toes) are phalanges (singular = phalanx). There are three phalanges in toes 2-5 and two phalanges in the great toe (digit 1). The three phalanges of the toes are named proximal, middle, and distal. The two phalanges of the great toe are named proximal and distal.

Question 15

What are the joints of the foot?

Answer 15

Small synovial joints are located between the bones of the foot. Metatarsophalangeal joints (MTPJ) are located between the metatarsals and the proximal phalanges and interphalangeal joints (IPJ) are located between the phalanges.

Question 16

What are the joint of the toes?

Answer 16

The great toe contains only two phalanges and so there is only one joint between them – this is the interphalangeal joint of the great toe (IPJ). Toes 2-5 contain three phalanges and so there are two joints between them: the proximal interphalangeal joint between the proximal and middle phalanx (PIPJ) and the distal interphalangeal joint between the middle and distal phalanx (DIPJ).

Question 17

What is the movement of the toes?

Answer 17

● Flexion and extension
● Abduction (moving the toes apart) and adduction (bringing the toes together).

Question 18

What is the imp of movement at the MTP joint?

Answer 18

Flexion at the MTP joints, especially the MTP joint of the great toe, is important for pushing the foot off the ground and forward propulsion during walking and running.

Question 19

What is the ankle joint like?

Answer 19

The ankle is a synovial hinge joint formed by the articulation between the distal tibia, distal fibula, and the talus. The socket formed by the tibia and fibula for the talus is called the ankle mortise. The malleoli use this mortise to ‘grip’ the talus. The joint is stable and supported by strong medial and lateral ligaments.

Question 20

What movements occur at the ankle joint?

Answer 20

There two movements that occur at the ankle joint are:
● Dorsiflexion (bringing the toes closer to the shin).
● Plantarflexion (pointing the toes).
Note that there is no ‘extension’ of the ankle joint, only two different types of flexion. Both are vital for normal gait.

Question 21

What movements occur at the ankle joint?

Answer 21

There two movements that occur at the ankle joint are:
● Dorsiflexion (bringing the toes closer to the shin).
● Plantarflexion (pointing the toes).
Note that there is no ‘extension’ of the ankle joint, only two different types of flexion. Both are vital for normal gait.

Question 22

What key ligaments for the lateral aspect of the ankle joint?

Answer 22

Three and they all attach to the lateral malleolus. They are the anterior talofibular, posterior talofibular and the calcaneofibular. However, we will simply think of them as the lateral ligaments of the ankle.

Question 23

What ligaments support the medial aspect of the ankle joint?

Answer 23

Several ligaments support the medial aspect of the ankle joint. They all attach to the medial malleolus. We can think of them simply as the medial ligament of the ankle; this is often also referred to as the deltoid ligament, because of the overall shape of the ligaments as a group.

Question 24

What is the subtalar joint?

Answer 24

This joint is formed by the articulation of the talus with the calcaneum and navicular. It is at this joint that inversion and eversion of the foot takes place.

Question 25

What occurs at the subtalar joint?

Answer 25

Inversion and eversion are important in allowing us to walk on uneven ground.
● Inversion brings the sole of the foot medially.
● Eversion raises the lateral border of the foot and brings the sole of the foot laterally.
● Forced inversion and eversion often sprain the ligaments of the ankle.

Question 26

What occurs in a tibial fracture?

Answer 26

High energy forces are required to fracture a healthy tibia. When the tibia fractures, the broken ends of the bone may break through the skin because there is little subcutaneous tissue between the anterior surface of the tibia and skin. If a there is broken skin overlying a fracture, or the bone penetrates out through the skin, it is called an ‘open’ or ‘compound’ fracture. Open fractures must be managed carefully to prevent infection from entering the exposed bone and ensuring the skin heals over the surface.

Question 27

What is Intra-osseus vascular access?

Answer 27

In critical emergency situations, where vascular access is required immediately to provide life-saving treatment directly into the bloodstream, and there is difficulty or delay in accessing peripheral veins, vascular access can be gained through the bone. The flat antero-medial part of the proximal tibia is a common site for IO access. A small handheld drill is used to ‘drill’ a cannula into the bone, and into the medullary cavity, providing a route to give treatment.

Question 28

What causes an ankle sprain?

Answer 28

Ankle sprains are very common and almost always result from a forced inversion of the foot. Forced inversion stretches and tears the lateral ligament of the ankle, resulting in pain and swelling over the lateral aspect of the ankle and foot

Question 29

What does ankle fracture refer to?

Answer 29

An ankle fracture refers to a fracture of the lateral and/or medial malleolus. Small lateral malleolus fractures, depending on their exact location, may be treated conservatively (without surgery). However, medial malleolus fractures and more proximal lateral malleolus fractures, or fractures with a dislocation of the ankle joint will require surgical fixation.