MR imaging assessment of the lateral head of the gastrocnemius muscle: prevalence of segmental anomalous origins in children and young adults.
BACKGROUND
Variations in the lower extremity musculature have been identified, including an anomalous origin of the medial head of the gastrocnemius muscle. Anomalies of the lateral head of the gastrocnemius muscle (LGN) have been less frequently described, especially in children.


OBJECTIVE
To describe the MR imaging appearance, frequency and clinical symptoms associated with anatomic variations of the LGN in children and young adults.


METHODS
A retrospective review of 465 knee MR imaging examinations was performed. The site of origin of the LGN was identified as either normal, lateral segmental anomalous origin (LSAO), or medial accessory anomalous origin (MAAO). The clinical indication for imaging was recorded.


RESULTS
An anatomic variation of the LGN was identified in 16 patients (3.4%). Nine patients had LSAO, and five of these had symptoms referable to or abnormalities of the patella. Seven patients had MAAO, and three of these had chronic nontraumatic knee pain.


CONCLUSIONS
Anatomic variations of the LGN are not rare in young patients, occurring with a frequency of 3.4% in our series. It is unknown whether these anomalies play a role in the etiology of patellofemoral pain or unexplained joint pain in children.
Kim
Hee Kyung
HK
Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229-3039, USA.
Laor
Tal
T
Racadio
Judy M
JM
D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007719:Knee Joint / Q000002:abnormalities* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000002:abnormalities* / Q000473:pathology*; D009139:Musculoskeletal Abnormalities / Q000453:epidemiology*; D015588:Observer Variation; D015995:Prevalence; D012189:Retrospective Studies; D017678:Sex Distribution; D055815:Young Adult