Musculoskeletal Anatomy - Lower Limb

Question 1

Why are the bones of the lower limb more massive than those of the upper limb?

Answer 1

They are more massive to support the stress of locomotion and greater weight bearing

Question 2

Why is the pelvis considered a composite structure?

Answer 2

It contains bones of both the axial (sacrum and coccyx) and the appendicular skeleton (hip bones).

Question 3

Which 3 bones make up each pelvic (aka coxal, innominate, or hip) bone? What cartilage separates them as children?

Answer 3

Ileum, ischium, and pubis. Separated by hyaline cartilage

Question 4

What differences between the male and female pelvis allow childbirth?

Answer 4

A female pelvis has:

• broader pubic arch, with the angle inferior to the pubic bones generally being greater than 90 degrees
• an enlarged pelvic outlet
• less curvature on the sacrum and coccyx
• wider, more circular pelvic inlet
• relatively broad, low pelvis
• ilia that project more laterally than in the male pelvis

Question 5

Fully classify the joint between the two pubic bones of the pelvis

Answer 5

Amphiarthrotic cartilaginous symphysis joint

Question 6

What are 3 functions of the patella

Answer 6

1) strengthen quadriceps tendon
2) protect anterior surface of knee joint
3) serve as anatomical pulley that increases contraction force of quadriceps femoris

Question 7

Why is the fibula smaller and thinner than other leg bones?

Answer 7

It bears minimal body weight (maybe 10%)

Question 8

What bony structures make up the ball of the foot?

Answer 8

The phalanges and metatarsal bones

Question 9

Why does it make sense for the pubic symphysis joint to be partially moveable

Answer 9

Childbirth - the baby’s head and body have to fit through

Question 10

Fully classify the sacroiliac joint. What cartilage covers the articulating surfaces?

Answer 10

• Diarthrotic synovial multiaxial planar joint

- Hyaline cartilage

Question 11

Which joint is a common site of lower back pain?

Answer 11

The sacroiliac joint

Question 12

Fully classify the hip joint and list the movements allowed

Answer 12

Diarthrotic synovial triaxial ball and socket joint

Adduction, abduction, flexion, extension, circumduction, rotation

Question 13

What are the functions of the medial and lateral menisci of the knee?

Answer 13

1) Act as cushions
2) conform to the shape of articulating surfaces as femur changes position
3) increase surface area of tibiofemoral joint
4) provide lateral stability to the joint

Question 14

What are the functions of the anterior and posterior cruciate ligaments?

Answer 14

1) limit anterior and posterior movement of femur

2) maintain alignment of femoral and tibial condyles

Question 15

What is the function of the medial and lateral collateral ligaments and when are they the tightest?

Answer 15

reinforce medial and lateral surfaces of the knee. Tightest when knee is in extension

Question 16

Fully classify the tibiofemoral joint and list the movements allowed:

Answer 16

• diarthrotic synovial monaxial hinge joint

- flexion, extension, some rotation

Question 17

Fully classify the talocrural joint and state which movements are allowed:

Answer 17

Diarthrotic synovial monaxial hinge joint

Allows dorsiflexion and plantarflexion.

Question 18

Fully classify the proximal, middle, and distal tibiofibular joints

Answer 18

Proximal: diarthrotic synovial multiaxial planar joint

Middle: amphiarthrotic fibrous syndesmosis joint

Distal: partial diarthrotic synovial multiaxial planar, partial amphiarthrotic fibrous syndesmosis.

Question 19

What type of bone is the patella?

Answer 19

Sesamoid

Question 20

Which two major connective tissues (tendon and ligament) attach at the patella?

Answer 20

• patellar ligament

- quadriceps tendon

Question 21

Why is it difficult to walk if you fracture your fibula even though it is not part of the knee joint?

Answer 21

The fibula is a site of attachment for many muscles, so when it is broken the muscles cannot attach properly and therefore cannot function properly. The fibula also helps to stabilize the ankle joint.

Question 22

What is the function of the sacroiliac joint?

Answer 22

To dissipate the load of the torso and pelvis

Question 23

Approximately how much of the femoral head fits into the acetabulum? What else helps to stabilize this structure?

Answer 23

• approximately 50% of the head
• four broad ligaments: ischiofemoral, iliofemoral, pubofemoral, and transverse acetabular ligaments. The ischio-, ilio-, and pubofemoral ligaments are all regional thickenings of the capsule

Question 24

The articulate capsule is further deepened by the ___________. This helps stabilize the head in the acetabulum.

Answer 24

• acetabular labrum

Question 25

What are the two anterior ligaments of the hip joint? In what position are they the most taut?

Answer 25

- pubofemoral and iliofemoral ligaments | - most taut in extension and abduction

Question 26

Which is the posterior ligament in this capsule? What movement does this ligament limit?

Answer 26

- ischiofemoral ligament | - limits extension and internal (medial) rotation

Question 27

What is the role of the ligament of the head of the femur?

Answer 27

- minimal role in joint stabilization - tenses when thigh is flexed and undergoing external rotation - location of blood vessels to head of the femur

Question 28

Why are hip dislocations relatively uncommon and what tends to occur instead?

Answer 28

- the head of the femur is enclosed by an almost complete bony socket, a strong articulate capsule, and is surrounded by stout supporting ligaments and dense muscular padding to make it a very stable joint. - fractures of the femoral neck are more common than hip dislocations

Question 29

What type of hip dislocation is most common?

Answer 29

- posterior hip dislocation

Question 30

Why is the knee not a very stable joint compared to the hip?

Answer 30

The hip has lots of muscle mass as well as bone on bone articulation to keep the femur in the socket of the acetabulum. The knee has some support from ligaments and muscles but not to the same extent as the hip

Question 31

Which joint allows the largest range of motion of the lower limb?

Answer 31

The knee - up to 160 degrees

Question 32

Fully classify the patellofemoral joint and list the movement(s) allowed:

Answer 32

Diarthrotic synovial multiaxial planar joint. Allows gliding motion

Question 33

What is the purpose of the fat pads and bursae in the knee joint?

Answer 33

Provide padding around the margins of the knee and reduce friction between the patella and other tissue.

Question 34

What movements do the medial, lateral, anterior, and posterior ligaments of the knee (respectively) limit?

Answer 34

Medial: limits medial displacement of the tibia relative to the femur Lateral: limits lateral displacement of the tibia relative to the femur Anterior: limits anterior displacement of the tibia relative to the femur. Posterior: limits posterior displacement of the tibia relative to the femur.

Question 35

When is the ACL tightest? When is the PCL tightest?

Answer 35

ACL: when knee is in extension PCL: when knee is in flexion

Question 36

Which ligament is most commonly injured and why?

Answer 36

ACL is more commonly injured because we spend more time standing with our knee in extension.

Question 37

How do ACL injuries occur and how can we prevent them?

Answer 37

Generally occur in high contact sports due to contact when the foot is planted and there is an impact from the side or when there is a sudden change in direction, sudden deceleration, or awkward landing. These injuries can be prevented by keeping some flexion in the knee so that the ACL is not stretched as extensively.

Question 38

What is the function of the two popliteal ligaments?

Answer 38

to reinforce the back of the knee joint

Question 39

How does the knee lock and why does it do this?

Answer 39

The knee locks in extended position when slight lateral rotation of the tibia tightens the ACL and jams the meniscus between the tibia and femur. The knee locks to allow us to stand for prolonged periods of time without using and tiring the extensor muscles.

Question 40

How does the knee unlock?

Answer 40

Contraction of the popliteal muscle initiates slight medial rotation of the tibia to begin flexion of the knee.

Question 41

In which position do most ankle injuries occur and why?

Answer 41

Most ankle injuries are due to an excessive amount of inversion during plantar flexion (rolling the ankle). This position uses more of the range of motion of our ankle but this leads to the tradeoff of a loss of stability in the joint. This most often causes damage to the lateral ligaments of the ankle.

Question 42

Which articulation of the ankle is the primary site for weight bearing?

Answer 42

The tibiotalar joint

Question 43

Which 3 joints provide medial and lateral stability at the ankle?

Answer 43

1) proximal tibiofibular joint 2) distal tibiofibular joint 3) fibulotalar joint

Question 44

What is the function of the tibiofibular ligaments?

Answer 44

- primary stabilizer of the ankle | - limit external rotation of the foot and sital fibular motion on the tibia

Question 45

What is the primary function of the lateral ligaments?

Answer 45

- limit anterior or posterior displacement of the talus and resist inversion

Question 46

Which ligaments of the ankle are most commonly sprained?

Answer 46

The anterior talofibular ligament is most commonly sprained. When in plantar flexion, this ligament is most taut and therefore most vulnerable.

Question 47

What is the main function of the deltoid ligament of the ankle?

Answer 47

Reinforce the ankle joint and help resist eversion