Blumensaat's line is a linear shadow on lateral X-rays of the knee that corresponds to the roof of the intercondylar notch between the two rounded condyles of the femur.
Page updated January 2024 by Dr Sheila Strover (Clinical Editor)
Blumensaat's line in cruciate ligament surgery
The lateral X-ray allows the two condyles to be lined up clearly identifying with a shadow where the roof of the notch lies. The shape of the notch roof is relevant to the surgeon doing an anterior cruciate ligament reconstruction.
Blumensaat's line in patella alta
Extending the line to beyond the X-ray shadow of the patella (kneecap) gives an indication of whether or not the patella is abnormally high or low, as it would normally intersect the lower pole of the patella.
"[Graft tunnel mismatch] is particularly problematic when bone–patellar tendon–bone....grafts are used, due to a potential compromise in fixation of the bone plug on the tibia....The Blumensaat line....will accurately approximate the native ACL....length and may aid in the prevention of [this problem]."
Citation: Joyner PW, Mills FB 4th, Brotherton S, Bruce J, Roth T, Hess R, Wilcox CL, Leddon CE, Davis B, O'Grady C, Andrews JR, Roth CA. Blumensaat Line as a Prediction of Native Anterior Cruciate Ligament Length. Orthop J Sports Med. 2020 Aug 6;8(8):2325967120943185. doi: 10.1177/2325967120943185. PMID: 32821762; PMCID: PMC7412920.