Department of Podiatry

Extrinsic Factors

Outline

- structural anomalies in thefemur / knee / tibia

- developmental conditions, not 'abnormalities'

- discrepancy exists in literature

- 'normal' values

- age of resolution

- effect on foot function

- largely theoretical - little research available

- frontal plane: inclination: coxa vara and valga

- transverse plane: femoral version and position

- sagittal plane : anterior convexity of femur

Femoral inclination - frontal plane alignment of head and neck of femur relative to shaft - at birth = 135-140 degrees - gradually reduces with development to the adult norm of 126 degrees - if it reduces too much, coxa vara results - if reduction is inadequate, coxa valga results - coxa vara leads to genu valgum - coxa valgaleads to genu varum

Femoral position - transverse plane angulation of head and neck of femur at the acetabulum - ante = internal, retro = external - at birth, 60° external - adult, decreases to 10° (ie: undergoes internal rotation) - insufficient - the hip will lie in an abnormal external position - excessive - the hip will lie in an abnormal internal position (picture at right - birth should read: BIRTH 60° external, ADULT 10° external)

Knee & Tibia development

knee joint

frontal plane

genu valgum / varum

sagittal plane

genu recurvatum / flexed knees

transverse plane

genicular position

Tibia

frontal plane

tibial varum / valgum

transverse plane

tibial torsion

Knee (frontal plane)

genu varum

associated with development, pathology of physes of knee

leads to tibial varum

Fully, partially, or un-compensated REARFOOT VARUS

genu valgum

associated with heriditary, physiology (development, pregnancy), or local factors (weight/obesity, trauma, infection)

causes a wide base of gait

CoG of limb passes medial to talus, favouring STJ pronation

large pronatory torque (ie, force times lever arm) acting on STJ

Development of tibiofemoral angle frontal plane

Newborn: 15° varus, 2 year old: rectus, 3 year old: 10° valgus, > 5 year old : slightly valgus

Knee (sagittal plane)

Sagittal plane

Genu recurvatum

hyperextension of the knee joint

commonly associated with generalised ligamentous laxity

Effects on foot function?

(will be accompanied by STJ supination

may lead to lateral instability > inversion ankle sprains, etc.)

Flexed knees

due to hamstring contracture

may occur in conjunction with gastrocnemius equinus

knee unable to reach full extension, which predisposes the knee joint to pathology such as PFS

Knee : Genicular Position

- transverse plane

- otherwise known as 'pseudolack of malleolar torsion'

- describes the transverse plane relationship between the tibia and knee joint

- Infants/young children:normal total range of motion (internal + external rotation) is 45° (full knee flexion), 0-20°(knee extension)

- By age 4 years: little rotation in extended knee

- can be abnormally internal (medial) or external (lateral)

- result of muscles and ligaments acting at knee joint

- Contracture of medial ligaments/muscles - internal

- Contracture of lateral ligaments/muscles - external

- at birth, internal genicular position exists due to:

intra-uterine confinement

increased range of knee joint rotation

muscular factors

- this internal position normally resolves with development, however if:

deformity is too severe, or:

resolution is incomplete,

... an internal genicular position persists

- Tibia will function in an internally rotated position

- Medial rotation of the tibia on the femur:

popliteus, semitendinosus, semimembranosus, sartorius, gracilis

- Lateral rotation of the tibia on the femur: lateral head of biceps femoris

- Internal genicular position

there is less than 10° of external rotation available at the knee joint

there is twice as much internal as external rotation available at the knee joint

- External genicular position

relatively rare

chronic lateral force applied to knee joint

neurological disorders

'W-sitting'

Tibia: Tibial version/rotation

transverse plane

a 'twist' in the tibial shaft between the proximal and distal ends

at birth, MM and LM on frontal plane, ie: zero degrees of version

during normal development, external torsion occurs until the tibia is 20-25 degrees externally rotated

if this does not occur to the normal degree, intoeing may result

if excessive rotation occurs, out-toeing may result

clinically, malleolar position (tibiofibular rotation) is used as an indicator of tibial torsion (M 5°< T)

0° increases to 25°

Functional implications

- all the transverse plane pathologies(ie: femoral version/torsion, femoral position genicular position, tibial version/torsion) combine to produce an external or internal position of the limb
- this affects the angle of foot placement
- pathologies in other planes (ie: genu varum / valgum, flexed knees / genu recurvatum) have specific associated pathomechanics

Internal limb position (transverse plane) can be caused by:
excessive femoral anteversion (called antetorsion)

internal femoral position

internal genicular position

inadequate malleolar version (called antetorsion)

...or a combination of each

- the foot is adducted (intoed)
- leg's CoG passes lateral to long axis of the foot
- STJ pronates to abduct the forefoot which brings the CoG closer to the long axis of the foot


External limb position (transverse plane) can be caused by:
lack of femoral anteversion (retrotorsion)

external femoral position

external genicular position

excessive malleolar version (retrotorsion)

...or a combination of each

- foot is abducted (out-toed)
body's CoG passes medial

to the talus, favouring STJ pronation

pronation torque (F times lever arm) increased (ie, lever arm)

- developmental anomalies may occur in the femur, knee joint or tibia
- may occur in any of the three planes
- due to excessive or inadequate rotations
- all have an effect on foot function

Need to knownormal adult values & effect on foot function

References

DeValentine SJ (1992) Foot and ankle disorders in children. Churchill Livingstone, New York, pp. 277-285.

Sgarlato TE (1971) A compendium of podiatric biomechanics. CCPM, San Francisco, pp. 15-33.

Links to relevant web pages

For more information on transverse plane limb alignment, follow the link to the MedNet hip pages.

Content Approved by: Head of Podiatry
Page maintained by: Podiatry Webmaster
Last Updated: August 20th, 2002