Patella Luxation Flashcards
What is the extensor mechanism of the stifle composed of? (5)
Quadriceps m
Patella
Trochlea
Patellar ligament
Tibial tuberosity
What articulation facilitates stifle extension?
Femoropatellar articulation
What bone type is the patella?
Sesamoid bone
What tendon is the patella located within?
Insertion of the quadriceps m
What bone does the patella articulate with?
Femoral trochlea
What are present on each side of the patella which articulate with the trochlear ridges?
Parapatellar fibrocartilages
What is patellar luxation a result of?
Mal-allignment of the extensor mechanism, such that the tremendous force of the quadriceps causes abnormal “tracking” of the patella; leading to (sub)luxation
What “type” of condition is patella luxation?
Development
How common is traumatic patella luxation?
Rare
What primary abnormalities have been proposed? (2)
Altered angles of inclination and version of the femoral neck
Define anteversion
Leaning forwards e.g. femoral neck leaning forward
Coxa vara:
- What is the degree of anteversion?
- Which way does the patella luxate?
A) decreased. <120
B) Medial
What is the normal femoral neck angle?
120-135 degrees
Coxa valga:
A) What is the degree of anteversion?
B) Which way does the patella luxate?
A) >135
B) lateral (although one studied found medial risk)
During normal development, how does the patellar groove to deepen and widen.?
The presence of the patella normally exerts pressure on the trochlear groove while growing
If patella luxation is present from an early age, what is the result on the trochlea?
Hypoplastic + shallow
Or absent
(as the patella has not been exerting pressure)
What is the effect of recurrent luxation and reduction of the patella (instability) on the trochlea ridge?
What cartilage also erodes?
Erosion with shallowing –> easier luxation
Articular cartilage
Is external femoral torsion normally present with medial or lateral patellar luxation?
Medial
Is lateral bowing of the tibia normally present with medial or lateral patellar luxation?
Lateral
Is coxa vara normally present with medial or lateral patellar luxation?
Medial
Is internal rotation of the foot normally present with medial or lateral patellar luxation?
Medial
Is coxa valga normally present with medial or lateral patellar luxation?
Lateral
Is hypoplastic lateral femoral condyle normally present with medial or lateral patellar luxation?
Lateral
Medial patellar luxation:
A) Effect on distal femur?
B) General effect on legs?
C) Trochlear groove?
D) Medial trochlear ridge?
A) Medial bowing
B) Genu varum (bow legs)
C) Shallow
D) Poorly developed/absent