1. MedPix Medical Image Database COW - Case of the Week Case Contributor: Mark M Morton Affiliation: Naval Medical Center Portsmouth

2. MedPix No: 9749 - History Pt Demographics: Age = 24 y.o. Gender = woman 24-year-old woman presents with left knee pain. No history of trauma. Downloaded by (-1)

3. MedPix No: 9749 - EXAM & LABS Afebrile. The skin overlying the left knee is intact without erythema, ecchymosis or abnormal warmth. No medial or lateral joint line tenderness. No joint effusion. No laxity to varus and valgus stress. Negative McMurray*s and Appley*s grind tests.

4. Osteochondroma AP and lateral plain radiographs of the left knee demonstrate a 2.5 cm long cortically-based osseous protuberance arising from the medial aspect of the distal femur and pointing away from the adjacent knee joint. Both plain radiographs demonstrate that the osseous protuberance is continuous with the medullary canal and cortex of the femur. Downloaded by (-1)

5. Osteochondroma AP and lateral plain radiographs of the left knee demonstrate a 2.5 cm long cortically-based osseous protuberance arising from the medial aspect of the distal femur and pointing away from the adjacent knee joint. Both plain radiographs demonstrate that the osseous protuberance is in continuity with the cortex and medullary cavity of the distal femur. Downloaded by (-1)

6. Osteochondroma This is an axial T1 SE image of the distal left fumur. Magnetic resonance images demonstrate that the osseous protuberance is continuous with the medullary canal and cortex of the femur. A cartilaginous cap is demonstrated on magnetic resonance imaging without evidence of abnormal enhancement or soft tissue mass or invasion. Downloaded by (-1)

7. Osteochondroma This is an axial T1 SE fat supressed image of the distal left femur. Magnetic resonance images demonstrate that the osseous protuberance is continuous with the medullary canal and cortex of the femur. A cartilaginous cap is demonstrated on magnetic resonance imaging without evidence of abnormal enhancement or soft tissue mass or invasion. Downloaded by (-1)

8. Osteochondroma This is an axial T2 FSE fat supressed image of the distal left femur. - - AP and lateral plain radiographs of the left knee demonstrate a 2.5 cm long cortically-based osseous protuberance eminating from the medial aspect of the distal femur and pointing away from the adjacent knee joint. Both plain radiographs and magnetic resonance images demonstrate that the osseous protuberance is continous with the medullary canal and cortex of the femur. A cartilaginous cap is demonstrated on magnetic resonance imaging without evidence of abnormal enhancement or evidence of soft tissue mass or invasion. Downloaded by (-1)

9. Osteochondroma This is an axial T2 FSE fat-suppressed image of the distal left femur. - - AP and lateral plain radiographs of the left knee demonstrate a 2.5 cm long cortically-based osseous protuberance eminating from the medial aspect of the distal femur and pointing away from the adjacent knee joint. Both plain radiographs and magnetic resonance images demonstrate thaat the osseous protuberance is continuous with the medullary canal and cortex of the femur. A cartilaginous cap is demonstrated on magnetic resonance imaging without evidence of abnormal enhancement or soft tissue mass or invasion. Downloaded by (-1)

10. Osteochondroma This is a gadolinium-enhanced axial T1 SE fat-suppressed image of the distal left femur. - - AP and lateral plain radiographs of the left knee demonstrate a 2.5 cm long cortically-based osseous protuberance eminating from the medial aspect of the distal femur and pointing away from the adjacent knee joint. Both plain radiographs and magnetic resonance images demonstrate thaat the osseous protuberance is continuous with the medullary canal and cortex of the femur. A cartilaginous cap is demonstrated on magnetic resonance imaging without evidence of abnormal enhancement or soft tissue mass or invasion. Downloaded by (-1)

11. FINDINGS AP and lateral plain radiographs of the left knee demonstrate a 2.5 cm long cortically-based osseous protuberance eminating from the medial aspect of the distal femur and pointing away from the adjacent knee joint. Both plain radiographs and magnetic resonance images demonstrate this lesion is continous with both the medullary canal and cortex of the femur. A cartilaginous cap is seen on MRI without evidence of abnormal enhancement, nor soft tissue mass, nor invasion.Knee Anatomy:http://rad.usuhs.mil/rad/anatomy/knee_gross.html

12. DIFFERENTIAL DIAGNOSIS What is your Differential Diagnosis? Osteochondroma

13. Diagnosis: Osteochondroma Dx Confirmed by: Characteristic plain radiographic and magnetic resonance imaging findings.

14. DISCUSSION None.