Q3: Biomechanics & Components Proximal to the Knee Flashcards
Knee: Type of Joint and Inhibitors
Joint:
* Modified Hinge Joint (2-6 DOFs)
Limiters:
* Menisci
* Ligaments/Muscles
Main Knee Motion
Sagittal Plane (Flex and Ext)
Initial Contact
Knee Mechanics
Approaching neutral; extensors are active
0 degrees
Midstance
Knee Mechanics
Slight flexion; extensors are active
0 degrees
Terminal Stance
Knee Mechanics
Approaching neutral
0 degrees
Preswing
Knee Mechanics
Rapid flexion is initiated
40 degrees flexed
Hip: Type of Joint and Inhibitors
Joint:
* Ball & socket
Limiters:
* socket depth
* muscles/ligaments
Acetabulum
Hip Joint
Acetabular labrum - fibrocartilaginous rim
Transverse ligament - closes the upside down “U”
Capitis femoris ligament - limits adduction
When standing…
Hip Forces and ligaments
0.3x bodyweight
When standing on 1 limb…
Hip Forces and ligaments
2.4-2.6x bodyweight
When walking…
Hip Forces and ligaments
1.3-5.8x bodyweight
When running…
Hip Forces and ligaments
4.5+ times bodyweight
Ligamentous Support
Hip ligaments
Iliofemoral (Y-lig)
* strongest in the body
Ishiofemoral
* limits ext. and abduction
Pubofemoral
Parastance
Hip Forces
standing using GRF; moves it posteriorly
Inital Contact
Hip Mechanics
Flexed 30 degrees; extensors active
Midstance
Hip Mechanics
Close to neutral; abductors active for balance
If abductors are weak, Trendelenberg will be (+)
Terminal Stance
Hip Mechanics
Extended 10 degrees
Preswing
Hip Mechanics
Rapid Flexion Initiated
Early/Mid Swing Phase
Hip Mechanics
Flexion continues; Flexors are active
Terminal Swing
Hip Mechanics
Hamstrings are active to slow tibia and prevent excessive hip flexion
Antalgic Gait
Hip Joint
Painful Hip may cause…
* PF for shock absorption
* Flex., Abduct, external rot. combo - optimize femoral head position
* pivot met. heads to avoid forceful push off in late stance
Initial Contact
GRF
Ankle - PF
Knee - Ext.
Hip - Flex
Loading Response
GRF
Ankle - PF
Knee - Flex
Hip - Flex
Midstance
GRF
Ankle - DF
Knee - Ext.
Hip - Ext.
Terminal Stance
GRF
Ankle - DF
Knee - Ext.
Hip - Ext.
Preswing
GRF
Ankle - DF
Knee - Flx
Hip - Ext
Goals
KAFO
- Control tibia and femur
- correction
- prevention
- muscle compensation
- increase stability
- decrease pain
Sagittal Indications
KAFO
- Quads MMT - 3+ or less
- Genu Recurvatum - > 30 degrees
- Knee flexion contractures
Coronal Indications
KAFO
Genu varum and valgum
Transverse Indications
KAFO
Rotary and/or triplanar instability
Other Indications (not plane of motion related)
KAFO
Proprioception or Sensory impairment
Types/Styles
KAFO
Conventional, Thermoplastic, Hybrid
Thermoplastic
KAFO
Increased contact, cosmesis, control
Decreased weight
Common Components
Conventional KAFO
- Proximal thigh band
- Distal thigh band
- Knee joints/Sidebars
- Calf band
- Ankle joints
Types of Ankle Joints
KAFO
- Double action
- Dorsi assist - swing phase help
- Free motion - coronal control
- Limited motion - stops PF
Solid Stirrups
KAFO
Direct attachment to shoe
Strong - continuous piece of metal
Can be hard to align mech. and anatomical joints
Split Caliper Stirrup
KAFO
Not as strong as solid (3 parts)
Easier to align
Can use multiple shoes
Hybrid AFO NYUCBL
Increased foot control while avoiding proximal contact
T-Strap
KAFO components
Address pronation or supination based on orientation
Sup. - attached laterally
Pron. - attached medially
Straight Knee Joints
Knee Joints
Uses ring/drop locks with a ball retainer; used for patients with UE issues
Swiss/Cam/French Lock
Knee Joints
Hands free lock; uses a bail release
Can disengage accidentally
Posterior Offset Joints
Knee Joints
Mech. joint is set posteriorly to provide knee stability
Indicated for hyperextention
Allows for flexion is swing phase
Dial Lock
Knee Joints
adjustable for knee deformities/contractures
Step (Ratchet) Lock
Knee Joints
hands free with incremental locking; self adjusts to available knee ROM
Key Lock
Knee Joints
Like a step lock but only locks in full extension
Stance Control KAFOs
- Free flexion in swing phase
- Locked knee in stance phase
Weight line shifts anterior to the knee after temporal midstance
Usually locked from IC to Midstance
Ankle Driven
Stance Control KAFO
Requires DF at Mid to Terminal stance to unlock
Cannot be used with solid ankle
Positional
Stance Control KAFO
Locks/Unlocks based on tibial inclination and hip positon
can be overly safe; knee can unlock early going downhill
Microprocessor
Stance Control KAFO
based on MP prosthetic knee technology; expensive
Spreader Bars
KAFO components
Controls hip motion when using B/L KAFOs
Axial Resist KAFO
Uses prosthetic principles to load limb proximally
Weight through:
* Ischial Tuberosity
* Scarpa’s triangle
Locked knee
Indications
Axial Resist KAFO
- Malunion
- Fx distal to midshaft of femur
- post-op
- arthritic conditions
Indications
Hip Orthoses
- Dysplastic disorders
- Trauma
- Post-Op
Unilateral or Bilateral Pelvic Bands
Hip Ox Components
- Midpoint from Iliac Crest to Greater Troch
- Rigid portion is 33% of circumference
- Anterior trimline - 30mm medial ASIS
- Posterior trimline - posterior midline
Free Motion
Hip Joints
Free sagittal motion;
controls coronal and transverse motion
Ring (Drop) Locks
Hip Joints
Hold in all planes
Trigger Lock
Hip Joints
Automatic locking
Adjustable (Dial) Lock
Hip Joints
Used when variable sagittal ROM is needed; 6 degree increments
Abduction-Flexion Joint
Hip Joints
used when variable sagittal/coronal ROM is needed
Indications:
* S/P hip replacement
* Hip dislocation
* lumbar fusion
Twister Cables
Transverse Hip Motion
Controls hip rotation; attaches to a pelvic band and shoe
Usually in small children
Contraversial
Walk About/Up & About Systems
Articulation proximal and medial to anatomical hip joint
* facilitate reciprocating gait but not forward progression
Landmarks
HKAFO
- Iliac Crest
- ASIS
- Greater Trochanter
- Anatomical Hip Joint
Anatomical Hip Joint
12 mm anterior & 25 mm proximal to the greater trochanter
Advantages of Crossing the Hip
- Increase coronal control
1. adductor issues - Increase transverse control
1. int./ext. rotation issues
Rationale
HKAFO
- Allow weight bearing (contracture prevention)
- Seat femur in acetabulum
- delay deformites (pediatrics)
- Post-Op
- stability
- transverse control
Usually short term and unilateral
Paraplegic Patient Goals
HKAFOs
- Therapeutic
- Improve Independence
- Hold alignment
- achieve external stability
Swing to/through
HKAFOs Gait Possibilities
Most efficient pattern
Swivel Walking
HKAFOs Gait Possibilities
Very slow but easy; may not require aids
Reciprocal Walking
HKAFOs Gait Possibilities
- Appears more normal
- Increased stability
- Less energy consumption, but more training
Standing Frames
Static HKAFOs
- SCI L3 or higher
- Need to have head control and seated balance
- Independent standing (FREE HANDS)
- Gravity affects bone density/GI tract
- reduces contractures
Parapodium
Static HKAFOs
Mech. Hip & Knee joints for sit to stand
* independent mobility
* swivel walker adaptation can be used
ORLAU Swivel Walker
Static HKAFOs
No joints; Swivels by laterally shifting weight
* allows for forward progression
* adjustable growth
* used only on flat ground
Connection methods
RGO
Reciprocating Gait Ox
1. Isocentric Bar
2. Double Cable
3. Single Push-Pull System
Ambulatory Progression
RGO
- Lateral shift
- Trunk extension
- Contralateral leg advancement
- Lateral shift
- repeat
gait training is important
Common Assistive Devices
RGO
Lofstrand Crutches
Indications
RGO
- Spina Bifida
- Paraplegia
- Atrophy
- MS
- CP
- Polio (not common anymore)
Contraindications
RGO
- contractures
- spasticity
- poor UE strength
- obesity
- ulcers
- poor bone density
- poor conditioning (cardio)
- lack of motivation/support/compliance
- hemiplegia
Advantages
RGO
Independent Locomotion;
Gravitational Benefits
Disadvantages
RGO
Expense,
issues with clothing,
and difficulty don/doffing
Gait Training Ox
GTO
Provides pelvic and trunk support; pt. can move hips and legs to facilitate progression
Indications
GTO
- CP
- Developmental Delay
- Step ability when unweighted
- Low weight (<74 lbs)
- plantigrade feet
- knee contractures up to 20 degrees
- stable hips
Contraindications
GTO
- Contractures
- Spasticity
- Lack of motivation, support
- Poor cognitive skills
Benefits
GTO
- Hands-free mobility
- guidance and control
- independence increases
- improves bowel/bladder function
- improves bone density
- self esteem and social interaction
Alignment and Fit
GTO
- Flat heel and sole with ground
- joint congruency (mech. and anat.)
- horizontal joint axis
- adequate confromity to pt. anatomy
Trimline Criteria
KAFO
- 35mm distal to perineum
- 10mm distal to troch.
Knee clearance: - medial - 6mm
- lateral - 3mm
Fitting Criteria
KAFO
- Distal thigh & calf strap = equal distance from knee center
- min. 105 degrees knee flexion
- If thermoplastic, then Total Contact fit
- If conventional, then 3-6mm clearance
- If conventional ankle, then 5-6mm clearance
Use appropriate foot plate length
