Injection of the pes anserine bursa and medial collateral ligament bursa

A 64-year-old woman presented with bilateral medial knee pain that woke her up at night. She was unable to climb stairs due to pain in the left knee. She had mild genu varum, and passive motion of the left knee revealed coarse crepitus. With the legs extended, there was marked tenderness in the bilateral medial knees. When the leg was flexed at 45 degrees, the findings differed between the knees, as shown in the four panels. She received injections in both knees with subsequent improvement in pain and her ability to climb stairs.
(A) Right knee. A circle marks the tibial (medial) collateral ligament, and the shaded area indicates the location of the anserine bursa. The tenderness to palpation was localized to the anserine bursa.
(B) Right knee. The anserine bursa was injected with a mixture of lidocaine and glucocorticoid.
(C) Left knee. The tenderness was localized to the tibial collateral ligament, marked with a circle. There was no tenderness to palpation over the anserine bursa, marked by the shaded area.
(D) Left knee. The region of the tibial collateral ligament-medial meniscus was injected with a mixture of lidocaine and glucocorticoid.