Lecture 7 - Hip Biomechanics (part 2) Flashcards
What are the groupings for the muscles that move the hips?
- Flexors
- Extensors
- Abductors
- Adductors
- Rotators (lateral/medial)
What are the hip flexors?
- Psoas major
- Iliacus
- Psoas minor
What does the psoas major do?
- Anterior to medio-lateral axis
- During quiet standing, contraction creates a flexion moment -> counters mass of upper body
What are the effects of psoas major weakness?
Large weakness alters late stage of stance (pre swing)
What are the effects of psoas major tightness?
Decreased hip extension rom -> limits trunk side-bending flexibility
What does the iliacus do?
- Large muscle with PCSA > psoas major
- Can be considered on part of the iliopsoas muscle
What are the effects of iliacus weakness?
- Similar to psoas major
- Can activate to prevent hip hyperextension
What are the effects of iliacus tightness?
- Anterior pelvic tilt
- Hyperextension of the lumbar spine
- Forward lean
What does the gluteus maximus do?
- PCSA 30% > iliopsoas
- Contributes to support during forward lean
- Contributes to hip abduction and adduction (change depending on position)
What are the effects of gluteus maximus weakness?
Gluteus maximus lurch:
- Rapid hyperextension of the trunk around heel contact
- Moves com posterior to hip joint
What are the effects of gluteus maximus tightness?
- Decreased hip flexion rom
- Decreases hip medial rotation rom
What are the hip abductors?
- Gluteus medius
- Gluteus minimus
What do the gluteus medius and minimus do?
Gluteus medius:
- Powerful abductor
Gluteus minimus:
- PCSA < gluteus medius
- Deep muscle
Combination:
- Essential role in closed-chain actions
- Stabilization of the pelvis
What are the effects of gluteus medius + minimus weakness?
Trendelenburg gait/gluteus medius lurch (lean to support side)
What are the effects of gluteus medius + minimus tightness?
Results in decreased adduction rom
What are the hip adductors?
- Pectineus
- Adductor brevis
- Adductor longus
- Adductor magnus
What is the function of the hip adductors?
- Stabilize pelvis during weight shifting
- Stabilize the hip during squats
What is the effect of hip adductor weakness?
Gait instability
Who is more likely to experience hip adductor tightness?
Common in sedentary individuals
What are the lateral rotators of the hip?
- Piriformis
- Obturators (internus/externus)
- Gamelli (superior/inferior)
- Quadratus femoris
What is the effect of lateral rotator weakness?
Difficult to detect
What is the effect of lateral rotator tightness?
Could exert pressure of the sciatic nerve
What are the muscles that do medial rotation?
- No muscle has main action of medial rotation
- Provided by secondary actions of other muscles (gluteus medius and minimus, piriformis, etc)
