Figure. Anteroposterior radiograph of left hip.
A 45-year-old man presents with severe left hip pain and difficulty flexing his hip. Two days ago he hyperextended his hip when he fell on ice. On physical examination, the patient has tenderness to palpation over the anterior inferior iliac spine that is made worse with resisted hip flexion. Radiography of the left hip shows an avulsion fracture of the anterior inferior iliac spine (Figure 1).
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The pelvis acts as an attachment site for the hip flexor muscles. Hip flexors include psoas major that attaches to the lesser trochanter, rectus femoris that attaches to the anterior inferior iliac spine (AIIS), and sartorius that attaches to the anterior superior iliac spine. The muscles of the quadriceps include the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Of the 4 muscles of the quadriceps, the rectus femoris is the most commonly injured and the only muscle that crosses the hip and knee joints.1
Avulsion of the AIIS can occur with a sudden forceful contraction of the quadriceps including a fall that hyperextends the hip joint or abrupt kicking motion.2 Diagnostic workup includes anteroposterior (AP) radiography, which will show the classic avulsion pattern. Magnetic resonance imaging (MRI) may be warranted if no obvious bony involvement or concomitant injury is suspected.1
Rectus femoris avulsion injuries are almost always treated nonoperatively with a period of rest and avoidance of hip flexion. Pain and function usually improve at 6 to 8 weeks after injury and patients can often return to sports or heavy labor at that time.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.
1. Begum FA, Kayani B, Chang JS, Tansey RJ, Haddad FS. The management of proximal rectus femoris avulsion injuries. EFORT Open Rev. 2020;5(11):828-834. doi:10.1302/2058-5241.5.200055
2. Knapik DM, Trasolini NA, Diaz CC, Chahla J, Forsythe B. Avulsion injuries and ruptures of the proximal rectus femoris in skeletally mature, high-level athletes: a critical analysis review. JBJS Rev. 2021;9(7). doi:10.2106/JBJS.RVW.20.00269