Left knee pain when bendi...

A 38-year-old woman comes to the hospital complaining of left knee pain when bending and squatting for the past two months. On physical examination, she exhibits soreness to palpation over the anterior medial knee and no effusion. Deep knee flexion exacerbates her knee pain. There is a cyst on the medial femoral condyle on radiography (Figure 1) but no arthritic changes. Figure 2 depicts an osteochondral lesion with cyst formation at the medial femoral notch measuring 2 x 2.5 cm on magnetic resonance imaging of the left knee.