A 43-yr-old woman presented with the insidious onset of left groin pain for several months. She reported that her pain was sharp with an intensity of 5 of 10 and was primarily elicited during activities including squatting, prolonged sitting, and stair climbing. She also reported occasional Bclicking[ along the anterior aspect of the left hip associated with pain while extending the hip. Upon examination, passive range of motion of the hip was normal without gross swelling in the anterior hip region. Maximum tenderness was noted over the left anterior inferior iliac spine (AIIS) with appreciable snapping of a firm cord-like structure during extension and external rotation of the hip. The flexion, adduction, and internal rotation test was negative for femoroacetabular impingement. The Ely test (passive flexion of the knee in prone position and bringing the heel toward the buttock) was positive for tightness of the left rectus femoris muscle. A plain radiograph of the left hip was unremarkable except for calcification along the acetabular rim.Ultrasonography examination of the left hip was performed using an 8-to 15-MHz broadband linear transducer and a LOGIQ S8 scanner (General Electric Healthcare, Milwaukee, WI). A hyperechoic calcification, 1.3 Â 0.6 Â 0.9 cm in size, was appreciated in the direct head of the rectus femoris at the AIIS with increased vascularity on Doppler compatible with calcific tendinitis (Figs. 1, 2). There was no hip joint effusion or osteophyte and no other tendon pathologies noted. Her symptoms improved with nonsteroidal anti-inflammatory medications and stretching exercise, and there was no tenderness over the left AIIS at the 6-month follow-up.The authors were able to estimate the acuity of calcific rectus femoris tendinitis by additional Doppler examination and visualize the snapping structures by dynamic evaluation. 1,2 The audible or perceived snapping is mediated by either the direct head impinged against the overlying iliacus muscle or the indirect head of the rectus femoris surrounding the acetabular roof. 3 The involvement of the indirect head was reported to be more common with painful limitation of range of motion caused by the overlap of insertion of the indirect head with capsular attachment 3,4 ; FIGURE 1 Longitudinal ultrasonographic images of the rectus femoris muscle using an 8-to 15-MHz linear array probe showing hyperechoic calcification in the direct head of the rectus femoris at the AIIS.FIGURE 2 Transverse image of the direct head of the rectus femoris muscle showing calcification with increased vascularity at the level of the AIIS.e10Am.