• Patellar dislocation occurs when there
is no contact between the patella and
the trochlear groove.
• Patellar subluxation is a temporary, partial
dislocation of the patella from the
• Acute dislocations can occur with direct
trauma such as a fall or a direct blow to
the knee; however, most occur from a
noncontact mechanism, typically frequent
exposure to the primary mechanism of injury.
occur laterally, resulting in
severe disruption of the
extensor mechanism as a
result of the patella sliding
over the lateral portion of the
• Acute patellar dislocations account for
2% to 3% of all knee injuries.
• First-time dislocations with a history of prior subluxation are most observed in girls 10 to 17 years of age, but subluxations/dislocations are most often observed in young, athletic individuals.
• Younger children and preadolescents have higher rates of recurrence and
greater underlying mechanical risk factors.
• In those treated nonoperatively after
a one-time dislocation, up to 44% will
dislocate again and >50% will report
symptoms associated with recurrent
MECHANISM OF INJURY
Dislocation/subluxation most often
results from a noncontact, lower extremity
internal rotation and knee valgus stress
on a fixed distal extremity.
COMMON SIGNS AND
• Patients present with a vague anterior knee
pain and swelling, with complaints of giving
way with specific activities such as jumping
, running, or making quick stops and quick
changes in direction.
• In recurrent instability, symptoms are
typically episodic and long term.
• Quick stops
• Quick changes in direction
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