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Biomechanics & Rehabilitation > Lower Limb Biomechanics Revision > Flashcards

Lower Limb Biomechanics Revision Flashcards

1
Q

Define varus

A

Inward angulation of the distal segment of a bone or joint towards the midline

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2
Q

Define Varus Stress

A

Force being applied away from the midline, forcing the distal limb segment towards the midline

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3
Q

Define Valgus

A

Outward angulation of the distal segment of bone or joint away from the midline

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4
Q

Define Valgus Stress

A

Force being applied towards the midline, resulting in the distal limb segment being forced away from the midline

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5
Q

What is coxa vara?

A
  • When the angle between the femoral neck and femoral shaft is less than 120degrees
  • It can result in leg length being shortened
  • Adductors strength > abductor strength
  • Commonly caused by injury (#) or soft bone causing bending
  • smaller angle therefore leg angled TOWARD midline
  • RESULTANT FORCE is LESS than normal
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6
Q

What is Coxa Valga?

A
  • When the angle between the neck and shaft of femur is >135degrees
  • There is generally a wider hip range and a wider squat angle
  • Adductor strength
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7
Q

What gives the hip joint stability?

A
  • bone congruence
  • acetabular labrum (continuous, transverse ligament over the acetabular notch)
    ▶️ mainly avascular
    ▶️ presence of nociceptors
    ▶️ deepens acetabulum by 21% increases acetabular contact by 28% and limits extreme ROM
    ▶️ distributes impact of load and maintains negative pressure
  • very strong capsule
  • ligaments
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8
Q

What are the ligaments that increase stability in the hip?

A
  1. Iliofemoral ligament
    - strongest, taught in extension & relaxed in flexion
    - prevents pelvis tilting posteriorly in stance, limits extension, external rotation and Adduction in extended lower limb
  2. Pubofemoral ligament
    - probably the weakest, strengthens anteroinferior part of capsule
  3. Ischiofemoral ligaments
    - supports the capsule posteriorly
  4. Ligamentum teres
    - triangular in shape and flattened, implanted by apex into anterosuperior part of fovea capitis femoris and base either side of acetabular notch
    - has LITTLE role in STABILITY and little influence as a ligament past childhood
    - ligament tensed when thigh semi-flexed and externally rotated
  5. Zona orbicularis (annular ligament)
    - little role in stability
    - anteriorly blend with deep surface of iliofemoral ligament and gain attachment to the anterior inferior iliac spine
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9
Q

Where are the two weak points in the ligaments of the hip?

A
  1. Between ilio and pubofemoral ligaments

2. Between ilio and ischiofemoral ligaments

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10
Q

Which hip muscles take part in the hips rotator cuff?

A
  1. Piriformis - External Rotation
  2. Gemellus superior & inferior - external rotation
  3. Obturator internus - abduction and external rotation
  4. Obturator externus - Adduction and external rotation
  5. Quadratus femoris - Adduction and external rotation
  6. Gluteus Minimus - abduction and internal rotation
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11
Q

Which muscles flex the hip?

A 
Iliopsoas
Rectus femoris
TFL
Sartorius
Adductors
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12
Q

Which muscles extend the hip?

A

Inferior part of gluteus max
Gluteus medius
Gluteus minimus
Hamstrings

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13
Q

Which muscles addict the leg at the hip?

A

Adductor brevis, Magnus, longus
Pectineus
Gracilis

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14
Q

Which muscles abduct the leg at the hip?

A 
Gluteus medius
Upper portion of gluteus max
Gluteus minimus
Piriformis
TFL
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15
Q

Which muscles control internal rotation at the hip?

A

Gluteus minimus
Piriformis
Anterior gluteus medius
TFL

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16
Q

Which muscles control external rotation at the hip?

A

Deep external rotators
Piriformis
Posterior gluteus medius
Gluteus max

17
Q

What is the joint reaction force in the hip?

A

The compressive force experienced at the femeroacetabular articulation and it is the result of the need to balance the moment arms of the body weight with the pull of the hip abductors at the greater trochanter to maintain a level pelvis

18
Q

How can you decrease the joint reaction force at the hip?

A

Increase abductor strength
Using a cane in the opposite hand (lengthens lever arm and provides a force which counteracts the body load at he end of e lever arm)

19
Q

How do you work out joint reaction force at the hip?

A

Joint Reaction Force = Body Weight + Abductor Force

JRF is always higher than body weight

20
Q

What are the determinants of joint reaction force?

A

Body weight
Body weight moment arm
Abductor force (muscles)
Abductor force moment arm

21
Q

What are the keystones in the arches of the foot?

A

Medial longitudinal arch = talus
Lateral longitudinal arch = cuboid
Transverse arch = middle cuneiform

22
Q

What class of lever is the hip?

A

Class 1/First order lever

23
Q

What class of lever is the foot and ankle?

A

Second order/class 2

24
Q

What is the function of the foot and ankle?

A

Lever/propulsion
Shock absorption
Support

25
Q

Which part of the foot is loaded during the gait cycle?

A

Heel strike - lateral heel
Propulsion - lateral foot
Toe off - lateral ➡️ medial

26
Q

How is propulsion achieved in the foot?

A

Achieved at the foot by a combination of inertia and muscle activation (in particular the activation of Gastroc, soleus and tibialis posterior)

27
Q

What is the Windlass mechanism?

A

Describes the influence of the passive structures of the foot (mainly plantar fascia) to create supination with the foot.

Dorsi flexion of the hallux, leads to tension of the plantar fascia and locking of the metatarsal joint ready for propulsion

28
Q

Why is pronation important during the gait cycle?

A

It is critical to attenuate load

29
Q

What provides stability in the knee?

A
  1. Bony shape and meniscal attachment
    - lateral meniscus smaller and more U shaped
    - medial meniscus larger and more C shaped
  2. Strong ligamentous structures
    - cruciate ligaments
  3. Tendons acting as active ligaments
30
Q

Describe the knee during gait

A
  • TIBIA EXTERNALLY rotates during terminal extension PRIOR to HEEL STRIKE
  • results in INVERSION of the foot at the subtalar joint
  • knee FLEXION during LOADING phase allows TIBIAL INTERNAL rotation and thus foot PRONATION ➡️ shock absorption
  • during TERMINAL STANCE, EXTENSION again occurs resulting in tibial EXTERNAL ROTATION and resultant subtalar joint INVERSION creating a rigid lever for PROPULSION
31
Q

Describe 3 features of the hip joint

A
  • it’s a ball and socket joint
  • surrounded by powerful and well-balanced muscles
  • high level of mobility vs remarkable stability

Biomechanics & Rehabilitation (10 decks)

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