1. Background:
The frequency of appearance of anatomical variability in the terminal division of the popliteal artery (PA) is different according to the type of sample used, and ranges from 2% to 21%.
The PA locates 1,01cm behind to the lateral meniscus, which makes it vulnerable during surgical procedures. Iatrogenic injury to the PA or its terminal branches increases if anatomical variables are present.
Our aim is to review and describe variations in branching of the PA in a cadaveric sample and determine the risk of iatrogenic injuries to these vessels during routine knee surgery procedures.
2. Methods:
A sample consisting of 260 popliteal regions, corresponding to 130 corpses (66 women, 64 men), have been dissected. Multivariate analysis was carried out.
A review of the current literature was done, and the different branching patterns of the popliteal artery were rearranged in a new easier and usefull classification.
3. Results:
The terminal division of the PA was classified as follows:
Pattern 1: the PA was divided into the anterior tibial (ATA) and the posterior tibial arteries (PTA) at the level or distal to the lower border of the popliteal muscle (PM) (94.7%).
Pattern 2: the PA bifurcated into the ATA and PTA, proximal to the lower border of the PM (3.3%). In this pattern, 3 different possibilities of bifurcation and travel of the vessels where found, and they where named as 2.a, 2.b, and 2.c.
Pattern 3: the PA divides at the same level into the ATA, PTA and PEA. (2%).
No significant differences between gender and side of the limb were found regarding the pattern of terminal division of the PA.
4. Discusion:
Some anatomical variables are particularly vulnerable during surgical procedures around the knee, such as the ATA in pattern 2b in sutures of the lateral meniscus, posterior cruciate ligament reconstructions, proximal tibial osteotomies or total knee arthroplasties. The incidence of the pattern 2b ranges from 0%-2.4% in the current literaure performed with cadaveric simples. In these cases, the ATA runs through the anterior surface of the PM, just behind the posterior cortex of the proximal tibial surface, and 1mm posterior to the joint capsule behind the posterior horn of the lateral meniscus. Knowing the vulnerability of the ATA in several surgical procedures around the knee if this pattern is present,, knee surgeous should recognize the vessels and their pathways when studying the MRI of their patients.
5. Conclusions:
We purpose a classification that encloses only three easily identifiable groups. This will allow clinicians to know about these variables and avoid injuries during surgical procedures as lateral meniscus repair. This is particularly relevant in the case of the pattern described as 2b.

Conflict of interests
The authors declare that they have no conflict of interests.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.