(BMJ)—A man in his 40s noticed a mass in his R anterior upper thigh 2 weeks after playing a soccer game. He had experienced sudden pain while kicking the ball. He quit playing but could walk. Pain improved, but the mass persisted. He resumed soccer 6 weeks postinjury. Exam: firm mass that moved proximally with leg extension. What’s the dx?
Rectus femoris tear
Malignant fibrous histiocytoma
Nerve sheath tumor
You are correct. The consistency of the anterior thigh mass was the same as that of the adjacent contracted vastus medialis and vastus lateralis and moved proximally with contraction of the quadriceps. Dx was confirmed with U/S showing rectus femoris tear and proximal migration of the rectus femoris muscle belly. The rectus femoris is more susceptible to injury than the other 3 quad muscles because it crosses both the hip and knee joints and, in the terminal phase of a kick (hip extended and knee flexed), undergoes forceful eccentric contraction while being passively stretched. Other space-occupying lesions (benign or malignant) seldom move with quad action unless they’re intramuscular.

Surgery isn’t indicated if full function and muscle strength (as in this case) are present. Conservative tx with analgesics, PT, and training to resume sports activity can be considered. Surgical repair is recommended for complete tears of the rectus femoris when functional limitation and muscle weakness occur. The patient was treated nonoperatively with PT. At 38-month follow-up, he remained well.

BMJ 2022;378:o1513