Lower Limb Stability and Muscle Action

Question 1

HIP

standing

posterior sway

anterior sway

Answer 1

Standing

• Extension at hip resisted by
  
  • Iliofemoral ligament
  • Ischiofemoral ligament

Posterior Sway

• Extension at the hip resisted by
  
  • Iliofemoral ligament
  • Ischiogfemoral ligament
  • Hip flexors
    
    • Iliopsoas
    • Rectus femoris

Anterior Sway

• Flexion at the hip resisted by
  
  • Hamstrings
    
    • Semimembranosus
    • Semitendonosus

Question 2

HIP

standing

posterior sway

anterior sway

Answer 2

Standing

• Extension at hip resisted by
  
  • Iliofemoral ligament
  • Ischiofemoral ligament

Posterior Sway

• Extension at the hip resisted by
  
  • Iliofemoral ligament
  • Ischiogfemoral ligament
  • Hip flexors
    
    • Iliopsoas
    • Rectus femoris

Anterior Sway

• Flexion at the hip resisted by
  
  • Hamstrings
    
    • Semimembranosus
    • Semitendonosus

Question 3

HIP

standing

posterior sway

anterior sway

Answer 3

Standing

• Extension at hip resisted by
  
  • Iliofemoral ligament
  • Ischiofemoral ligament

Posterior Sway

• Extension at the hip resisted by
  
  • Iliofemoral ligament
  • Ischiogfemoral ligament
  • Hip flexors
    
    • Iliopsoas
    • Rectus femoris

Anterior Sway

• Flexion at the hip resisted by
  
  • Hamstrings
    
    • Semimembranosus
    • Semitendonosus

Question 4

KNEE

standing

psoterior sway

anterior sway

Answer 4

Standing

• Extension at the knee resisted by
  
  • Posterior joint capsule of the knee

Posterior

• Flexion at the knee resisted by
  
  • Knee extensors
    
    • Quadriceps femoris

Anterior

• Extension at the knee resisted by
  
  • Posterior capsule of knee
  • Knee flexors
    
    • Biceps femoris
    • Semimembranosus
    • Semi-tendinosus

Question 5

KNEE

standing

posterior sway

anterior sway

Answer 5

Standing

• Extension at the knee resisted by
  
  • Posterior joint capsule of the knee

Posterior Sway

• Flexion at the knee resisted by
  
  • Knee extensors
    
    • Quadriceps femoris

Anterior Sway

• Extension at the knee resisted by
  
  • Posterior capsule of knee
  • Knee flexors
    
    • Biceps femoris
    • Semimembranosus
    • Semi-tendinosus

Question 6

KNEE

standing

posterior sway

anterior sway

Answer 6

Standing

• Extension at the knee resisted by
  
  • Posterior joint capsule of the knee

Posterior Sway

• Flexion at the knee resisted by
  
  • Knee extensors
    
    • Quadriceps femoris

Anterior Sway

• Extension at the knee resisted by
  
  • Posterior capsule of knee
  • Knee flexors
    
    • Biceps femoris
    • Semimembranosus
    • Semi-tendinosus

Question 7

ANKLE

standing

posterior sway

anterior sway

Answer 7

Standing

• Dorsiflexion at the ankle resisted by
  
  • Plantar flexors
    
    • Gastrocnemius
    • Soleus

Posterior Sway

• Plantar flexion at the ankle resisted by
  
  • Dorsiflexors
    
    • Tibilias anterior
    • Extensor digitorum longus

Anterior

• Dorsiflexion at the ankle resisted by
  
  • Plantar flexors
    
    • Gastrocnemius
    • Soleus

Question 8

ANKLE

standing

posterior sway

anterior sway

Answer 8

Standing

• Dorsiflexion at the ankle resisted by
  
  • Plantar flexors
    
    • Gastrocnemius
    • Soleus

Posterior Sway

• Plantar flexion at the ankle resisted by
  
  • Dorsiflexors
    
    • Tibilias anterior
    • Extensor digitorum longus

Anterior

• Dorsiflexion at the ankle resisted by
  
  • Plantar flexors
    
    • Gastrocnemius
    • Soleus

Question 9

Standing

Answer 9

Primary function of back and lower limb muscles is to:

• Maintain erect posture
• Prevent movement caused by gravity

Weight bearing > distal limb is fixed, proximal limb is movable

Non-weight bearing > distal limb movable, proximal limb fixed

Stability

• Line of gravity must pass through supporting base
  
  • Line of gravity
    
    • Vector connecting COG to the center of the earth
  • COG
    
    • All mass of object is concentrated
    • Anterior S2 in adult
• Widening gait/stance = wider supporting base = more stable
• Joint stability
  
  • No torque around axis
  • Line of gravity must pass through axis of rotation

Standing > Gravity causes:

• Extension at hip resisted by
  
  • Iliofemoral ligament
  • Ischiofemoral ligament
• Extension at the knee resisted by
  
  • Posterior joint capsule of the knee
• Dorsiflexion at the ankle resisted by
  
  • Plantar flexors
    
    • Gastrocnemius
    • Soleus

Question 10

Anterior Sway

Answer 10

Anterior Sway > Gravity causes

• Flexion at the hip resisted by
  
  • Hamstrings
    
    • Semimembranosus
    • Semitendonosus
• Extension at the knee resisted by
  
  • Posterior capsule of knee
  • Knee flexors
    
    • Biceps femoris
    • Semimembranosus
• Dorsiflexion at the ankle resisted by
  
  • Plantar flexors
    
    • Gastrocnemius
    • Soleus

Question 11

Posterior Sway

Answer 11

Posterior Sway > Gravity causes:

• Extension at the hip resisted by
  
  • Iliofemoral ligament
  • Ischiogfemoral ligament
  • Hip flexors
    
    • Iliopsoas
    • Rectus femoris
  • Gower’s Sign (common with Duchenne Muscular Dystrophy)
    
    • Lordotic shoulders displaced posteriorly > iliofemoral and ischiofemoral ligaments stabilize the hips
• Flexion at the knee resisted by
  
  • Knee extensors
    
    • Quadriceps femoris
• Plantar flexion at the ankle resisted by
  
  • Dorsiflexors
    
    • Tibilias anterior
    • Extensor digitorum longus

Question 12

Lateral Hip Stability

Answer 12

Lateral hip stability > Gravity causes (on supporting side)

• Adduction at the hip resisted by
  
  • Hip abductors
    
    • Gluteus medius
    • Gluteus minimus
• Gravity pulls pelvis on unsupported side > adduction
• Weak gluteus medius/minimus > pelvic drop > + Trendelenburg sign