L3 - Biomechanics of the hip and pelvic girdle Flashcards
Name the parts of the pelvis.
What do these parts form?
- Ilium, ischium, pubis
- Make up acetabulum
See NDC p.3 for illustration
Describe the hip joint.
- 2 parts
- type of joint
- degrees of freedom
- Proximal femur: Head is 2/3 of sphere + acetabulum
- Synovial, ball and socket (triaxial) joint
- 3 degrees of freedom
See NDC p.3 for illustration
Describe the hip muscles.
Surrounding large, strong muscles
Describe the ligaments of the hip joint.
- name
- location
- function (restricts…)
- Iliofemoral: located at front of hip + strongest
–> Hyperextension - Pubofemoral: anterior and inferior part of hip
–> Abduction, External Rotation - Ischiofemoral: posterior part of hip
–> Internal Rotation, Adduction, Extension
See NDC p.4 for illustration
What is the function of the labrum of the hip?
Fibrocartilaginous ring that deepens acetabulum.
See NDC p.4 for illustration
Describe the stability and mobility of the hip vs shoulder.
Why? (2)
Greater stability + less mobility (in hip vs. shoulder)
* Greater boney congruency (more contact)
* More support by ligament/capsule
What causes movement restriction in the hip? (3)
- ligaments
- muscles
- combination
Name the range of motion for movements in each plane.
- sagittal
- frontal
- transverse
Sagittal
- Flexion : 0~125°
- Extension: 0~15°
Frontal
- Abduction: 0~45°
- Adduction: 0~30°
Transverse
- External rotation: 0~45°
- Internal rotation: 0~45°
See NDC p.9 for illustration
What are the minimum ranges of motion for common activities.
- flexion
- abduction
- external rotation
Hip flexion: at least 120°
Abduction: at least 20°
External rotation: at least 20°
See NDC p.10 for examples of range necessary for activities
Describe the hip replacement.
- name
- reason
Hip replacement (arthroplasty) for:
- arthritis
- trauma
What are the movement restrictions after a hip replacement? (3)
Why?
See NDC p.12 for examples of adaptive equipment.
Restricted ROM after hip replacement (posterior or
lateral approach)
- No hip flexion > 90°: sitting
- No extremes of rotation: leaving feet on ground and turning trunk
- No adduction past midline
Ensure hip does not dislocate
Name the pelvis-hip interactions.
- Hip hiking-pelvic drop
- Forward/backward rotation
- Anterior/posterior pelvic tilt
Describe an anterior pelvic tilt VS posterior pelvic tilt.
- relative location of structures
- movement at hip
Anterior tilt: hip flexion
–> ASIS more anterior to pubic tubercle
Posterior: hip extension
–> ASIS more posterior to pubic tubercle
*ASIS = anterior superior iliac spine
See NDC p.14 for illustration
Describe hip hiking-pelvic drop.
- movement happening at each hip
Lower side = hip abduction
Higher side = hip adduction
See NDC p.15 for illustration
Describe forward/backward rotation.
- movement happening at each hip
Forward Innominate= hip external rotation
Back Innominate= hip internal rotation
See NDC p.16 for illustration
Name the spine-hip interactions seen in hip extension and flexion.
Hip extension
- extending hip and lumbar spine
- anterior pelvic tilt
Hip flexion
- flexing hip and lumbar spine
- posterior pelvic tilt
See NDC p.17 for illustration
Name the spine-hip interactions seen in hip abduction.
Hip abduction
- a lateral tilt of the trunk and pelvis
See NDC p.17 for illustration
Why is it important to know the spine-hip interactions?
Joints work together
1. When stretching, compensation can stretch different parts that are not the goal
2. In lack of range, an athlete may compensate with spine = pain
What “causes” hip flexion and extension during gait when the foot is on and off the ground?
When foot is in the air, flexion and extension of hip comes from the hip moving relative to the fixed pelvis.
When foot is on the ground, flexion and extension of hip comes from the trunk moving over the fixed femur.
See NDC p.18 for illustration
What “causes” hip adduction and abduction during gait when the foot is on and off the ground?
When foot is on the ground, the hip is adducting (single leg stance) to avoid the pelvis from dropping too much.
–> the pelvis is higher on the side of the grounded leg
When foot is in the air, the hip is abducting because the pelvis is lower on the side of the floating leg.
*hip hiking-pelvic drop
See NDC p.19 for illustration
What “causes” hip external and internal rotation during gait when the foot is on and off the ground?
When foot hits the ground, the hip is externally rotated
–> leg forward = pelvic rotates forward
As other leg swings, the grounded hip starts to internally rotate because the pelvic is rotating backward
When foot is about to go into air, other leg is extended
–> the pelvis on the grounded side is rotated backward = internal rotation of the hip
See NDC p.20 for illustration
What femoroacetabular impingement?
Describe what happens.
A condition affecting gait
- Extra bone growth in hip = Irregular shape =Poor fit
- Bones rub = Joint damage (degeneration of cartilage + labrum)
- Pain + activity limitations
See NDC p.21 for illustration
Name the 3 types of femoroacetabular impingement.
- Pincer-extra acetabulum bone
–> extra labrum over head - Cam-misshapen femoral head
–> femoral head is mishappen - Combined-both
See NDC p.21-22 for illustration
What can cause femoroacetabular impingement (FAI) in sports? (3)
- Cam deformity: common in soccer, ice hockey
- Overuse and excessive training (sport specialization*): loading leading to bone deformity
- Increase physical activity (self-report) leads to greater risk of hip pain in adults (20-49 of age)
*speculative
IR = internal rotation
What movements in soccer can cause problems (lead to femoroacetabular impingement (FAI)? (3)
- Hip flexion
- Adduction
- IR with kicking
*speculative
IR = internal rotation
What movements in hockey can cause problems (lead to femoroacetabular impingement (FAI)? (3)
Hockey*
- Push off: Hip extension, abduction with skating
- Recovery Hip flexion, adduction, IR with skating
- Butterfly goalies: Hip flexion, IR
*speculative
IR = internal rotation
See NDC p.24 for illustration
What is the treatment for femoroacetabular impingement (FAI)?
What are some of the outcomes? (2)
Surgery will remove extra bone and repair labrum
(hip arthroscopy)
Surgery can prevent hip degeneration/osteoarthritis
(somewhat) (Hunsen 2023)
Outcomes (research)
1. 78% of Swedish hockey players return to sport next
season (96% for professional players).
2. Only 28% played same number of games as pre-surgery. (Lindman 2022)
What is the impact of femoroacetabular impingement (FAI) on gait?
FAI may lead to decreased hip range of motion gait.
No difference in hip angles during gait.
See NDC p.26 for illustration
What is the angle of inclination of the hip joint?
What is a normal angle?
Angle between
- line going thru femoral head/neck
- line along the shaft of the femur
Normal: About 125°
See NDC p.27 for illustration
What is coxa vara?
Describe it. (3)
- limb length
- abductors
- femoral neck
Coxa vara <125°
1. Limb is shortened
2. Abductors are more effective
3. More bending of femoral neck
See NDC p.27 for illustration
What is coxa valga?
Describe it. (3)
- limb length
- abductors
- hip
- femoral neck
- predicts…
Cox valga >125°
1. Lengthens the limb
2. Reduces effectiveness of abductors
3. Changes loading in the hip (moves lateral, less area) = increases risk for degeneration
4. Also-more compressive loads on neck, less bending force
Maybe ish: it predicts the development of hip ostheoarthritis (degeneration) or severity
See NDC p.27 for illustration
Why are the abductor muscles less effective in coxa valga?
What does this extra force cause?
Reduces effectiveness of abductors by reducing moment arm.
The muscles need to do more work = greater joint reaction forces over less area.
See NDC p.27 for illustration
What is anteversion?
What is the normal angle at the hip joint?
Anteversion= angle in transverse plane
–> Neck-to-shaft angle
Normal: 15°
See NDC p.28 for illustration
What is excessive anteversion?
What is decreased anteversion?
Excessive anteversion: >15°
Decreased anteversion: <15°
See NDC p.29 for illustration
What can we see if excessive anteversion isn’t compensated for?
What is the compensation of the body?
How is it visible?
Without compensation: Femoral head will move anterior within the acetabulum
- toes are pointing externally
Compensation: hip internal rotation (to force femoral head back into the center of the acetabulum)
- toed-in
- patella facing inwards
See NDC p.30-31 for illustration
What is cerebral palsy?
What is it caused by?
What is seen in this condition?
Neurological condition
Caused by damage to the developing brain during
pregnancy or childbirth
Spaticity: resistance of muscles to movement
What can cerebral palsy cause? (2)
Can result in femoral anteversion: a condition where the femur (thigh bone) rotates outward (external rotation)
1. Hip subluxation/dislocation
2. Internally rotated hips during gait (to compensate for the external rotation, pushes hip back into socket)
What is a treatment for femoral anteversion in cerebral palsy?
Describe it.
What are the benefits? (3)
Femoral osteotomy
Cut proximal femur, realign femoral head in acetabulum, stabilize with pins/plates/rods
Benefits:
1. Improve alignment
2. Prevent deterioration/pain
3. Improve gait
Describe the forces acting on the hip when loading. (3)
- Hip loading causes a twisting action on the hip = moment
- Superior neck = tensile force
- Inferior neck = compressive force
See NDC p.37 for illustration
What is Wolf’s Law?
Bone will be organized to resisted applied loads
”Form follows function”
–> if an astronaut spends a lot of time in space, they will lose bone mass
” The trabecular system of the hip joint is the network of trabeculae, or bony struts, that make up the head and neck of the femur. The trabeculae grow in patterns that follow the lines of stress on the bone, with more trabeculae developing in areas of maximum stress.”
See NDC p.38 for illustration
Name the static hip forces. (3)
- Ground reaction force (Fw): wants to adduct the leg
–> creates and adduction moment (torque) - Abduction muscle movement (torque): Abduction muscles counteract this adduction by abducting the leg
- Hip joint reaction force = mathematical sum of everything we don’t know (labrum, capsule, muscles)
See NDC p.39 for illustration
Name the hip joint forces for single leg stance.
- abductor muscles forces
- hip joint reaction forces
- Abductor muscle forces 1.5 to 2 times body weight
- Hip joint reaction forces approximately 2.5 times body weight
Why is the hip joint reaction force much bigger than the abductor muscle force?
Partly due to differences in lever arms (smaller for abductor muscle force than for ground reaction force)
Can we change the lever arms for abductor muscle force and ground reaction force?
- Abductor muscle force – NO, attachment is fixed
- Ground reaction force - YES –> changing our stance
Describe the hip joint reaction forces when standing on two feet.
–> how much weight can the hip joint withstand?
Standing on two feet
- force = 30% of body weight (BW)
Describe the hip joint reaction forces when standing on one foot.
–> how much weight can the hip joint withstand?
- standing
- stairs
- walking
- running
Standing on one foot
- force increases = 2.5 to 3X BW
- stair climbing up to 3X BW
- walking from 4 to 7X BW
- running up to 10X BW
What is the max weight the hip joint can withstand?
The hip joint can withstand 12 to 15X bw before fracture or breakdown in the osseus component will occur.
What is the function of the hip abductor muscles in gait?
Hip abductor muscles (e.g. gluteus medius) balance the adduction moment (torque)
–> it controls the pelvis over the femur
What is trendelenburg gait/ gluteus medius lurch?
What causes it?
How is it recognizable?
Weakness in hip abductors (gluteus medius/minimus)
Often due to pain in the hip from disease (hip osteoarthritis)
Standing on affected leg, pelvis drops on unsupported
side
See NDC p.44-45 for illustration/video
What is the compensation for trendelenburg gait / gluteus medius lurch?
Why? (3)
Compensated by leaning upper body and trunk over
affected leg (lateral trunk lean)
- Decrease moment arm of the ground reaction force
- Less adduction torque
- Less hip abductor muscle force required
See NDC p.44-46 for illustration/video
