"Kinking is a variant of coiling and describes an elongated cervical ICA segment with an angulation less than 90°. Kinked ICA can be further classified based on the severity of angulation: Grade 1 (mild) is angled at 90°–60°, Grade 2 (moderate) at 60°–30°, and Grade 3 (severe) less than 30° [2, 3]."
http://www.hindawi.com/journals/crivam/2013/929530/

"Degradation and fragmentation of elastin as a consequence of age, cyclic mechanical stress and atherosclerotic arterial disease may contribute to decreased in situ axial pre-stretch, predisposing to more severe kinking of the artery during limb flexion and loss of energy-efficient arterial function."
http://www.ncbi.nlm.nih.gov/pubmed/25301303