McCarthy et al reviewed risk factors for patellar instability. This is often a multifactorial problem with risk factors that may change over time. The authors are from the University of Minnesota, William Beaumont Hospital, Oakland University and TRIA Orthopedic Center.
Risk factors for patellar instability:
(1) trochlear dysplasia
(2) patella alta
(3) increased lateral quadriceps vector
(4) genu valgum
(5) rotational deformity of femur (femoral anteversion, other)
(6) rotational deformity of the tibia (tibial torsion, other)
(7) tightness of the lateral retinaculum
The risk of recurrence increases with the number of risk factors present.
Femoral anteversion and patella alta tend to decrease with aging.
Tibial torsion and genu valgum tend to be stable after age 7 years.
Lateral quadriceps vector may increase with age.
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