Unit 3 - Biomechanics of lower limb

Question 1

What type of joint is the hip joint?

Answer 1

Ball (head of femur) & socket (acetabulum)

Question 2

What factors make the hip joint stable?

Answer 2

Ball & socket
Strong joint capsule
Ligaments & muscles

Question 3

What is the range of motion for the following movements in the hip:

• Flexion/extension?
• Abduction/adduction?
• External/internal rotation?

Answer 3

140/20

30/25

90/70 (less when hip is extended due to restrictive soft tissues)

Wide RoM in all 3 planes also allows circumduction (femur can move in circle relative to pelvis)

Question 4

How to calculate hip joint force during bipedal standing?

Answer 4

No muscles acting therefore only need to consider external forces - weight of upper body & 2 reaction forces at hip

Can use the fact that Σmoments = 0

Question 5

How to calculate hip joint force during unipedal standing?

Answer 5

Abductor muscles activated to stabilise position

4 forces to consider - weight of lower limb, abductor muscle force, joint force, ground reaction force

Question 6

Why is the hip joint force so much greater in unipedal standing than bipedal?

Answer 6

Contraction of abductors pulls to sides of hip joint together

Question 7

What 2 articulations make up the knee joint?

Answer 7

Tibiofemoral & patellofemoral

Question 8

Describe the menisci & their functions

Answer 8

2 crescent shaped pieces of fibrocartilage attached to tibia by short ligaments

Make top of tibia concave (stability), distribute load & absorb shock

Question 9

What is the depression between the femoral condyles called?

Answer 9

Trochlea (anterior)

Intercondylar notch

Question 10

What type of bone is the patella?

Answer 10

Sesamoid - bone found within a tendon

Patella is largest in body & is found in tendon of quadriceps femoris

Question 11

What factors aid stability of the knee?

Answer 11

Cruciates
Joint capsule
Collateral ligaments
Quadriceps
Menisci

Question 12

Describe the motion of the knee

Answer 12

Generally a hinge joint however axis of rotation changes in flexion/extension

Femoral condyles not perfectly circular or same size giving the knee a screw-home mechanism that follows a spiral motion:

• as knee flexes tibia rotates internally
• as knee extends tibia rotates externally

Question 13

What are the ranges of motion in the knee for:

• flexion/extension?
• internal/external rotation?

Answer 13

140/5

When at 90 flexion: 30/45
0 degrees when knee fully extended

Question 14

What is the function of the patella?

Answer 14

Assists knee extension by increasing lever arm of quadriceps muscle by displacing tendon

Lever arm of quadriceps femoris is dependent on position of patella which is dependent on degree of knee flexion (as knee flexes, patella sinks into trochlea and decreases length of lever arm)

Question 15

Why are menisci poor to heal?

Answer 15

Blood supply is only to peripheral edges

Question 16

What 3 articulations make up the ankle joint?

Answer 16

Tibiotalar, fibulotalar & distal tibiofibular

Question 17

What are the 3 most important ligaments in the ankle?

Answer 17

Anterior inferior talofibular (most commonly injured in sprain)
Medial
Lateral

Question 18

What is the range of motion of the ankle joint?

Answer 18

Dorsiflexion: 10-20

Plantarflexion: 25-35

Question 19

What bones make up the hindfoot?

Answer 19

Talus & calcaneus (os calcis)

Question 20

What bones make up midfoot?

Answer 20

Cuboid, navicular medial, intermediate & lateral cuneiforms

Question 21

What bones make up the forefoot?

Answer 21

Metatarsals & phalanges

Question 22

What motion does the subtalar joint allow?

Answer 22

Inversion (20)
Eversion (5)

Articulation between talus & calcaneus
Has oblique axis positioned at 42 degrees to plantar surface & 16 degrees to medial to mid-line of foot

Question 23

What arches are there in the foot?

Answer 23

Longitudinal

Transverse

Question 24

What is the function of the plantar fascia?

Answer 24

Heavy ligamentous structure extending from calcaneus to proximal phalanges that supports longitudinal arches

Works with bones of longitudinal arch to act as a truss, preventing downward force from body weight collapsing longitudinal arches

Shock absorber

Question 25

What happens to plantar fascia & foot when toes dorsiflex?

Answer 25

Fascia put under tension & 2 ends of foot are drawn together raising the longitudinal arch

Bones of foot held tightly together & function as single unit

Question 26

What is the term used to describe normal walking?

Answer 26

Reciprocal gait

Question 27

What are the sequential events in reciprocal gait?

Answer 27

Heel contact 
Foot flat
Mid stance
Heel off
Toe off
Mid swing

Question 28

State the RoM required in the sagittal plane for each of the joints in reciprocal gait

Answer 28

Hip:
  - flexion 30
  - extension 15
Knee (greatest RoM):
  - flexion 70 
 Ankle:
  - plantarflexion 15
  - dorsiflexion 10