Findings: The AP view of the knee demonstrates not only findings consistent with osteoarthritis but also a linear ossific density adjacent to the medial femoral condyle. This did not correlate to the patient's site of tenderness.

Diagnosis: Pellegrini-Stieda disease.

Discussion: Pellegrini-Stieda disease represents calcification or ossification of the medial collateral ligament at its insertion on the medial femoral condyle. This is a sequela of previous injury to the medial collateral ligament. It has been postulated that the calcification results from a knee sprain in which there is avulsion of the periosteum which subsequently ossifies or alternatively, the calcification may simply be calcification within a post traumatic hematoma.

Reference:
Harris JH, et al. Knee. In: The Radiology of Emergency Medicine.
Williams & Wilkins. Baltimore, Maryland; 1993:950-958.

Resnick D. Soft Tissues. In: Bone and Joint Imaging. W.B. Saunders, Co.,
Philadelphia; 1989:1280-1281.

Rogers LF. The Knee and Shafts of the Tibia and Fibula. In: Radiology of Skeletal
Trauma, Volume 2. Churchill Livingstone, New York; 1992:1223.

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