Hip pain · difficulty walking · tenderness along the anteromedial thigh and groin · Dx?

A 14-year-old Caucasian boy presented to our clinic with a complaint of left anterior hip pain. The patient had been running during a flag football match when he suddenly developed a sharp, stabbing pain in his left hip. He said he felt a "pop" in his left groin while his left foot was planted and he was cutting to the right. The patient said this was followed by worsening pain with ambulation and hip flexion. The patient had considerable difficulty walking into the exam room. On physical examination, he had significant tenderness to palpation along the anteromedial thigh and groin. The patient's strength was 1/5 with left hip flexion. There was apparent muscle firing, but no significant leg movement. He had full passive range of motion and there was no soft-tissue swelling, erythema, or other integumentary changes.