Can you demystify the medical term 'Pellegrini–Stieda syndrome' for me?
Pellegrini–Stieda syndrome (also called Stieda disease and Köhler–Pellegrini–Stieda disease) refers to the ossification of the superior part of the medial collateral ligament of the knee. It is a common incidental finding on knee radiographs.  It is named for the Italian surgeon A. Pellegrini (b. 1877) and the German surgeon A. Stieda (1869–1945).

References
Further reading
Altschuler, Eric L.; Bryce, Thomas N. (December 2006). "Images in clinical medicine. Pellegrini-Stieda syndrome". The New England Journal of Medicine. 354 (1): e1. doi:10.1056/NEJMicm040406. PMID 16394294.
Wang, JC; Shapiro, MS (1995). "Pellegrini-Stieda syndrome". American Journal of Orthopedics. 24 (6): 493–7. PMID 7670873.

External links
Whonamedit.com