Lecture 7 - Hip Biomechanics (part 2)

Question 1

What are the groupings for the muscles that move the hips?

Answer 1

1. Flexors
2. Extensors
3. Abductors
4. Adductors
5. Rotators (lateral/medial)

Question 2

What are the hip flexors?

Answer 2

1. Psoas major
2. Iliacus
3. Psoas minor

Question 3

What does the psoas major do?

Answer 3

• Anterior to medio-lateral axis
• During quiet standing, contraction creates a flexion moment -> counters mass of upper body

Question 4

What are the effects of psoas major weakness?

Answer 4

Large weakness alters late stage of stance (pre swing)

Question 5

What are the effects of psoas major tightness?

Answer 5

Decreased hip extension rom -> limits trunk side-bending flexibility

Question 6

What does the iliacus do?

Answer 6

• Large muscle with PCSA > psoas major
• Can be considered on part of the iliopsoas muscle

Question 7

What are the effects of iliacus weakness?

Answer 7

• Similar to psoas major
• Can activate to prevent hip hyperextension

Question 8

What are the effects of iliacus tightness?

Answer 8

• Anterior pelvic tilt
• Hyperextension of the lumbar spine
• Forward lean

Question 9

What does the gluteus maximus do?

Answer 9

• PCSA 30% > iliopsoas
• Contributes to support during forward lean
• Contributes to hip abduction and adduction (change depending on position)

Question 10

What are the effects of gluteus maximus weakness?

Answer 10

Gluteus maximus lurch:
- Rapid hyperextension of the trunk around heel contact
- Moves com posterior to hip joint

Question 11

What are the effects of gluteus maximus tightness?

Answer 11

• Decreased hip flexion rom
• Decreases hip medial rotation rom

Question 12

What are the hip abductors?

Answer 12

1. Gluteus medius
2. Gluteus minimus

Question 13

What do the gluteus medius and minimus do?

Answer 13

Gluteus medius:
- Powerful abductor
Gluteus minimus:
- PCSA < gluteus medius
- Deep muscle
Combination:
- Essential role in closed-chain actions
- Stabilization of the pelvis

Question 14

What are the effects of gluteus medius + minimus weakness?

Answer 14

Trendelenburg gait/gluteus medius lurch (lean to support side)

Question 15

What are the effects of gluteus medius + minimus tightness?

Answer 15

Results in decreased adduction rom

Question 16

What are the hip adductors?

Answer 16

1. Pectineus
2. Adductor brevis
3. Adductor longus
4. Adductor magnus

Question 17

What is the function of the hip adductors?

Answer 17

• Stabilize pelvis during weight shifting
• Stabilize the hip during squats

Question 18

What is the effect of hip adductor weakness?

Answer 18

Gait instability

Question 19

Who is more likely to experience hip adductor tightness?

Answer 19

Common in sedentary individuals

Question 20

What are the lateral rotators of the hip?

Answer 20

1. Piriformis
2. Obturators (internus/externus)
3. Gamelli (superior/inferior)
4. Quadratus femoris

Question 21

What is the effect of lateral rotator weakness?

Answer 21

Difficult to detect

Question 22

What is the effect of lateral rotator tightness?

Answer 22

Could exert pressure of the sciatic nerve

Question 23

What are the muscles that do medial rotation?

Answer 23

• No muscle has main action of medial rotation
• Provided by secondary actions of other muscles (gluteus medius and minimus, piriformis, etc)