Biomechanics

Question 1

Varum and valgum throughout development

Answer 1

Birth = genu varum (15-20 degrees) 
2-4 years = straight (0 degrees) 
4-6 years = genu valgum (5-15 degrees) 
6-12 years = straight (0 degrees) 
12-14 years = genu valgum (5-10 degrees) 
14+ years = straight (0 degrees)

Question 2

Ankle equinus

Answer 2

Less than 10 degrees dorsiflexion

Question 3

Ankle joint stable position

Answer 3

Ankle joint is most stable in maximally dorsiflexed position

Question 4

STJ axis

Answer 4

• 42 degrees from sagittal plane, 16 degrees from transverse plane
• Neutral position is 2/3 the distance from the most supinated position

Question 5

STJ ROM

Answer 5

• Average ROM is 25-30 degrees (highly variable)

- Minimum of 12 degrees is required for normal ambulation

Question 6

Femur ankle of inclination

Answer 6

Long axis of the neck vs long axis of the shaft

• Birth = 140 degrees
• Adults = 120-130 degrees

Question 7

Femur ankle of declination (antetorsion)

Answer 7

AKA angle of femoral torsion - long axis of neck vs coronal plane of distal condyles

• 1 year = 39 degrees
• Adult = 6 degrees

Question 8

Angle of anteversion

Answer 8

Long axis of neck of femur relative to pelvis

• Birth = 60 degrees
• Adult = 10-12 degrees

Question 9

Metatarsal length

Answer 9

Longest 
- 2
- 3
- 5
- 4
- 1
Shortest

Question 10

Metatarsal distal protrusion

Answer 10

Longest 
- 2
- 3
- 1
- 4
- 5
Shortest

Question 11

Bohlers angle

Answer 11

Angle between posterior to middle facet and anterior to middle facet of calcaneus

• Normal = 20-40 degrees
• Average = 30-35 degrees
• Decreases in calcaneal fracture

Bohler’s angle bottoms out

Question 12

Gissane’s angle

Answer 12

AKA critical angle or crucial angle - angle between middle facet to sinus tarsi and sinus tarsi to anterior facet

• Normal: 120-145
• Increases in calcaneal fracture

Gissane’s angle gets greater

Question 13

Fowler-Philip angle

Answer 13

Angle from posterior calcaneus to plantar calcaneus

• Normal = 44-69 degrees
• Pathology = >75 degrees

Question 14

Total angle

Answer 14

• Calcaneal inclination able + Fowler-philip angle

- Greater than 90 degrees may be observed in a Haglund’s deformity

Question 15

Parallel pitch lines

Answer 15

• Line across plantar calcaneus
• Line perpendicular to first line
• At dorsal calcaneus, draw line perpendicular to second line (parallel to first line)
• If the posterior tubercle of the calcaneus extends above the third line there is a Haglund’s deformtiy

Question 16

Meary’s angle

Answer 16

Lateral x-ray

• Straight line through mid axis of the talus and mid axis of the 1st metatarsal
• Normal = 0 degrees
• Mild flatfoot = 1-15 degrees
• Severe flatfoot = >15 degrees

Question 17

Calcaneal inclination angle

Answer 17

• Average 20-25 degrees
• Value does not change with pronation/supination
• Decreased in pes planus, increased in pes cavus

Question 18

Angle of Hibbs

Answer 18

Lateral x-ray

• Long axis of 1st metatarsal and long plantar axis of calcaneus (calcaneal inclination)
• Normal = 135=140
• Pes cavus = <150

Question 19

Kites angle

Answer 19

AP x-ray

• Long axis of talus and long axis of calcaneus
• Normal = 20-40 degrees
• Increased in pronation, decreased in supination

Question 20

Limb length discrepancy

Answer 20

A true LLD requires a 5 mm discrepancy to cause a significant functional and structural problem

• Shorter leg supinates
• Longer leg pronates
• Compensatory scoliosis by 13-14 years old

Question 21

Windlass mechanism

Answer 21

As the hallux is dorsiflexed, the plantar fascia is pulled under the head of the metatarsal. This brings the calcaneus toward the head of the 1st metatarsal, thereby creating an elevated medial longitudinal arch.

Question 22

SACH heel

Answer 22

• A rounded heel (rockerbottom)

- Allows more cushioned fluid motion through the heel contact phase of gait

Question 23

Cobra pad

Answer 23

• Prefabricated orthotic providing arch support and off-loading the heel
• Usually felt and easily fit into dress shoes

Question 24

Metatarsal bar

Answer 24

• Pad placed just behind metatarsal heads to reduce pressure on 2nd, 3rd and 4th met heads

Question 25

Denver bar

Answer 25

- Placed under metatarsal bones to support transverse arch of foot - Extends from metatarsal heads to TMTJ

Question 26

Dancer's pad

Answer 26

- Off-loads 1st metatarsal head | - Indications: sesamoiditis or fractured sesamoid

Question 27

Low-dye strap

Answer 27

- A strapping technique achieved with tape that alleviates the strain associated with pronation, particularly plantar fasciitis

Question 28

Spastic gait

Answer 28

- Internal rotation and adduction of entire limb - Flexion of hip, knee and ankle - Seen in cerebral palsy, familial spastic diplegia, paraplegia and hemiplegia

Question 29

Dyskinetic gait

Answer 29

- A constant movement abnormality with a high degree of variability - Motion involving considerable effort, often with deliberate almost concentrated steps - Seen in cerebral palsy, Huntington's chorea and dystonia muscular deformities

Question 30

Ataxic gait

Answer 30

- Marked instability during single limb stance with alternating wide/narrow base during double support - During swing, limb swings widely and crosses midline - Seen in MS, tabes dorsalis, diabetic polyneuropathy and Fredrich's ataxia

Question 31

Waddling gait

Answer 31

- Labored gait exhibiting difficulty with balance and pelvic stability - Lumbar lordosis - Seen in muscular dystrophies, spinal muscular atrophy and congenital dislocated hip

Question 32

Steppage gait

Answer 32

- Swing phase drop foot | - Seen in CMT, Guillain-Barre syndrom, CVA, paralytic drop foot and fascioscapulohumeral dystrphy

Question 33

Vaulting gait

Answer 33

- Gait changes include a high step rate, increased lateral trunk movement, scissoring and instability from step to step - Seen in myotonic dystrophy

Question 34

Equinus gait

Answer 34

- Ankle plantarflexion during swing phase with no heel contact - Seen in cerebral palsy, CMT, muscular dystrophy, spinal muscular atrophy, Schizophrenia, osseous block of ankle and habitual toe walkign

Question 35

Fenistrating gait

Answer 35

- Shuffling gait with loss of reciprocal arm swing, decreased velocity, decreased stride length and increase step rate - Seen in Parkinson's disease

Question 36

Trendelenberg gait

Answer 36

- Stance phase of each step leads to a contralateral tilt of the pelvis with a deviation of the spine to the affected side - Seen with dislocated hip or weakness of the gluteus medius muscle

Question 37

Calculate STJ neutral

Answer 37

- Add the amount of maximum eversion of the calcaneus from the bisection of the lower 1/3 of the leg and the maximum amount of inversion of the calcaneus from the bisection of the lower 1/3 of the leg - Next, take 1/3 of the total range of motion - Lastly, subtract this amount from the maximum amount of eversion