A 12-year-old boy is brought to the physician by his mother because of a 1-month history of pain below the left knee. His mother says, "He can usually walk around, but he hasn't been able to play in a

A 12-year-old boy is brought to the physician by his mother because of a 1-month history of pain below the left knee. His mother says, "He can usually walk around, but he hasn't been able to play in any of his soccer games since this all began." Examination of the left knee shows warmth, swelling, and tenderness. An x-ray of the knee is shown. Which of the following structures is attached to the abnormal anterior tibial area?