Knee Flashcards
Explain the ossification of the tibia and fibula.
- 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
Explain sagittal plane motion of the knee in a newborn.
- the knee of a newborn is flexed 30 degrees, and this flexion contracture reduces over 6 months
- cannot extend knee joint
What is considered tight hamstrings?
- anything under 55 degrees is considered pathological
Explain frontal plane development of the knee joint.
- newborn: 15-20 varum
- 6-12 months: 15-20 varum
- 18-24 months: neutral
- 3-4 years: 8 valgum
- 6-11 years: 6 valgum
When is peak genu varum?
6-12 months
When is peak genu valgum?
3-4 years
What is tibial torsion?
- A twist in the longitudinal axis of the tibia - internal or external
- can impact foot positioning
What type of gait would internal tibial torsion and external tibial torsion create?
Internal tibial torsion: in-toeing gait
External tibial torsion: out-toeing gait
Explain the transverse plane development of the tibia/knee.
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
How is knee extension measured?
Popliteal angle: take our normal hamstring measurement and minus it from 180
How is tibial torsion measured?
- Thigh foot angle: has problems as joints can move and alter results
- MRI
- History taking
What are the unexpected findings at the knee?
- genu varum
- genu valgum
- tibial torsion
- medial vehicular bias
What is genu varum?
- bow legs
- two different types considered outside of ‘age for stage’: physiologic and pathologic
- physiologic occurs without an underlying disease
Explain physiologic genu varum.
- 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
Explain pathologic genu varum?
- tibia vara (chondral error)
- physeal disruption post-trauma or infection
- metabolic bone disease
- generalised skeletal dysplasia
- focal fibrocartilagenous dysplasia
- diagnosed radiographically
What is genu valgum?
- 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
How do you treat genu valgum?
- 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
How is tibial torsion treated?
- 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
What are Dennis-Brown boots?
- 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
What is medial genicular bias?
- 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)
What type of gait may result from medial genicular bias?
An in-toeing gait
How is medial genicular bias treated?
- avoid ‘W’ sitting
- encourage activities that require external rotation of the feet
- can refer to a physio or exercise physiologist
How can you test for medial genicular bias?
- 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
