Fig. 3.

Bilateral superolateral infrapatellar fat pad (Hoffa fat pad) impingement in a 28 year-old woman with bilateral anterior knee pain due to patellar maltracking. Sagittal fat-suppressed proton-density MR images (A) of the right and (B) left knees show increased signal (arrow) in the superolateral aspect of Hoffa fat pad bilaterally. Note bilateral high-riding patella with modified Insall-Salvati index of 2.2: the distance between distal patellar articular surface and distal patellar tendon insertion (dashed double end arrow)/patellar length (solid double end arrow) is greater than 2. (C) 3D volume rendered image of both knees shows bilateral lateral patellar tilt (curved arrows), lateral patellar shift with and increased tibial tubercle –femoral trochlear distance (2 cm bilaterally) (double end arrows).