Abstract
We present an instructive case of habitual left patellar dislocation in which the patella had appeared odd due to lateral tilt relative to contralateral side, but had been radiologically confirmed to be on the trochlea at 1 year prior to the referral. An 11-year-old girl presented to our hospital 2 years after the left patella had dislocated with a 'giving way' when cutting to the left. Our physical and radiological examinations confirmed that the left patella was laterally tilted in the patellar groove with the knee in extension but was dislocated in flexion beyond 45°. In spite of these findings, she had been untreated at the previous hospital since all plain X-rays, including a skyline patellar view, had failed to demonstrate the dislocation. Consequently, in addition to reconstruction of medial patellofemoral ligament, she had to undergo a lateral retinacular release, which might have been unnecessary if treated earlier. This case illustrates that first-time patellar dislocation can gradually lead to habitual dislocation subsequently, and that cautious physical examinations in regard to patella tracking are essential since radiological examinations do not always reveal the pathophysiology of patellar instability.
Highlights
Acute patellar dislocation can result in anterior knee pain, recurrent dislocation and patellofemoral arthritis, but rarely in habitual dislocation, defined as a dislocation that occurs every time the knee is flexed [1]
We report a case of habitual patellar dislocation that appeared odd to the patient’s family due to lateral tilt compared with contralateral patella, but was left untreated because plain X-rays did not demonstrate significant patellofemoral malalignment 1 year prior to the referral
Since the deformity gradually became apparent, she was referred to our hospital. Her body height and weight belonged to the lower 10th percentile, she did not have any associated anomalies that present with patellar instability, such as Down syndrome [2] or Kabuki make-up syndrome [3,4]
Summary
Acute patellar dislocation can result in anterior knee pain, recurrent dislocation and patellofemoral arthritis, but rarely in habitual dislocation, defined as a dislocation that occurs every time the knee is flexed [1]. Case Report Two years prior to presentation to our hospital, an 11-year-old girl recognized that her left patella was dislocated with a ‘giving way’ when cutting to the left. She was capable of repositioning it by herself and saw an orthopedic surgeon who did not point out any skeletal abnormalities on plain X-ray. Since the deformity gradually became apparent, she was referred to our hospital Her body height and weight belonged to the lower 10th percentile, she did not have any associated anomalies that present with patellar instability, such as Down syndrome [2] or Kabuki make-up syndrome [3,4].
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