Knee

Question 1

Explain the ossification of the tibia and fibula.

Answer 1

• tibia and fibula begin to chondrify by the middle of the 6th week of gestation
• tibia begins to ossify two weeks later in the 8th week of gestation

Question 2

Explain sagittal plane motion of the knee in a newborn.

Answer 2

• the knee of a newborn is flexed 30 degrees, and this flexion contracture reduces over 6 months
• cannot extend knee joint

Question 3

What is considered tight hamstrings?

Answer 3

• anything under 55 degrees is considered pathological

Question 4

Explain frontal plane development of the knee joint.

Answer 4

• newborn: 15-20 varum
• 6-12 months: 15-20 varum
• 18-24 months: neutral
• 3-4 years: 8 valgum
• 6-11 years: 6 valgum

Question 5

When is peak genu varum?

Answer 5

6-12 months

Question 6

When is peak genu valgum?

Answer 6

3-4 years

Question 7

What is tibial torsion?

Answer 7

• A twist in the longitudinal axis of the tibia - internal or external
• can impact foot positioning

Question 8

What type of gait would internal tibial torsion and external tibial torsion create?

Answer 8

Internal tibial torsion: in-toeing gait

External tibial torsion: out-toeing gait

Question 9

Explain the transverse plane development of the tibia/knee.

Answer 9

newborn: neutral or medial
1 y.o: 5 external
Mid-childhood (8-10): 10 external
Older children: 14-20 external
Normal adult is approx. 15

Question 10

How is knee extension measured?

Answer 10

Popliteal angle: take our normal hamstring measurement and minus it from 180

Question 11

How is tibial torsion measured?

Answer 11

• Thigh foot angle: has problems as joints can move and alter results
• MRI
• History taking

Question 12

What are the unexpected findings at the knee?

Answer 12

• genu varum
• genu valgum
• tibial torsion
• medial vehicular bias

Question 13

What is genu varum?

Answer 13

• bow legs
• two different types considered outside of ‘age for stage’: physiologic and pathologic
• physiologic occurs without an underlying disease

Question 14

Explain physiologic genu varum.

Answer 14

• tibiofemoral angle of atlas 10 degrees varus
• normal growth plate
• apex of bowing at proximal end of tibia
• not an internal cause, look at external causes

Question 15

Explain pathologic genu varum?

Answer 15

• tibia vara (chondral error)
• physeal disruption post-trauma or infection
• metabolic bone disease
• generalised skeletal dysplasia
• focal fibrocartilagenous dysplasia
• diagnosed radiographically

Question 16

What is genu valgum?

Answer 16

• knock knees
• knock knees are normal until around age 3-4
• if persisting by 8 y.o. with little to no change in alignment requires investigation
• if put knees together and medial malleoli are more than 10cm apart - indicates knock knees
• pathologic = renal osteodystrophy, metaphysical dysplasia, Ollier’s disease

Question 17

How do you treat genu valgum?

Answer 17

• treat if pain with gait, cosmetic concern or KJ pain
• x-rays required if history of trauma, short stature, infection, asymmetry or metabolic bone disease
• if mild then treat by avoiding things that bring the knees together e.g. ‘W’ sitting

Question 18

How is tibial torsion treated?

Answer 18

• hard to treat
• can’t do casting, as bone is too big to twist and can cause skin irritations
• usually need surgery
• if a child - can try Dennis-brown boots

Question 19

What are Dennis-Brown boots?

Answer 19

• used to treat tibial torsion
• wear for as long as possible each day, and can wear them for years
• use in children who are too young to ambulate

Question 20

What is medial genicular bias?

Answer 20

• there is more medial rotation than lateral rotation at the knee
• in children there should be 1:1 or 1:2 med:lat rotation (so more lateral rotation than medial)

Question 21

What type of gait may result from medial genicular bias?

Answer 21

An in-toeing gait

Question 22

How is medial genicular bias treated?

Answer 22

• avoid ‘W’ sitting
• encourage activities that require external rotation of the feet
• can refer to a physio or exercise physiologist

Question 23

How can you test for medial genicular bias?

Answer 23

• clamp knee on bench, grab leg and twist each way to compare
• test extended and bent
• if there is a difference then tight hamstrings may be involved