CHAPTER 61 • SOFT TISSUE KNEE INJURIES (TENDON AND BURSAE) 359medially or anteromedially to correct tubercle
malalignment, as documented by an abnormal Q
angle). Moving the tibial tubercle medially (distal
realignment) cannot be performed before skeletal
maturity. Medial patellar instability is uncommon.
It occurs most commonly following previous
overly restrained lateral procedures.FRACTURES
•Patellar fractures are most commonly transverse in
orientation and are seen best on a lateral X-ray.
Vertical fractures are rare and best seen on the sunrise
view. Fracture types include undisplaced, transverse,
lower or upper pole, comminuted, and vertical.
Undisplaced fractures are treated nonoperatively with
6 weeks of bracing/casting in extension followed by
progressive range of motion exercises. Displaced frac-
tures are those with at least 3 mm of cortical disrup-
tion or 2 mm of articular step off on radiographs.
These are treated with open reduction internal fixa-
tion (ORIF). Fractures that occur with patellar dislo-
cation most commonly involve the lateral condyle or
medial patellar facet. With a traumatic avulsion of the
VMO in a previous normal knee, surgical repair and
early motion is advocated.
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(TENDON AND BURSAE)
John J Klimkiewicz, MDBIOMECHANICS OF TENDON
RUPTURES- Position of knee flexion of the knee directly affects
this ratio. At knee flexion angles < 45 °, this ratio is >1,
while at those a knee flexion angles >45 ̊ this ratio is
<1 (Huberti et al, 1984). - At greater than 45°, the patellar tendon has a mechan-
ical advantage and is less susceptible to injury through
tensile failure, while at positions less than 45°the
quadriceps tendon has a mechanical advantage and is
less vulnerable to injury.
•Tendon strain in response to tensile load is up to three
times greater at the insertion sites than at the tendon
midsubstance. Additionally, collagen fiber stiffness is
less at the insertion sites. These biomechanical
Extensor mechanism force ratio=Patellar tendon force
Quadriceps tendon force