Knee – Pigmented villonodular synovitis

CASE HISTORY

45-year-old man with pain and lump in the posterior knee and history of PVNS first removed with second surgery of the medial knee two year later.

TECHNICAL FACTORS

Long- and short-axis fat- and water-weighted images were obtained before and after contrast administration.  Contrast Type: Dotarem 7.5 mmol per 15 mL vial NDC 67684-2000-2. Contrast Amt: 16.

KEY IMAGES

This case has no key images.

CASE FINDINGS

• Multifocal diffusely penetrating medial and lateral facet class 4 chondromalacia patella. Relative trochlear sparing.
• Quadriceps and patellar tendons are noncontributory.
• 1 to 2+ effusion.
• Medial and lateral menisci unremarkable. Cruciates normal. Collaterals normal.
• No less than 14cm long is a large pigmented mass that follows the course of the gastrocnemius-semimembranosus bursa the semimembranosus bursa and the pes anserinus bursa. Findings are most compatible with PVNS. Given the size measurements previously this reader suspects that there has been substantive size increase and requests the prior images for direct comparison if possible.
• No bone marrow infiltration or encroachment on the femoral notch.
• The medial position has spared the popliteal artery vein and nerve although all are pushed laterally along with the medial gastrocnemius.

CASE CONCLUSION

14cm long area of pigmented villonodular synovitis involving the gastrocnemius-semimembranosus bursa the pes anserinus bursa and the semimembranosus bursa.