Classification of lower extremity venous malformations and risk of knee involvement: A retrospective cohort study.

Abstract Background Venous malformations (VM) are the most common vascular anomaly in the lower extremity. VM can be classified as focal, multifocal or diffuse types. Intraarticular VM (IA-VM) of the knee portends morbidity. Association of lower extremity VM type with IA-VM is not well defined. Objective To classify a large cohort of lower extremity nonsyndromic VM by type and determine associations with IA-VM. Methods: Retrospective cohort study. Results We assessed 156 patients with nonsyndromic lower extremity VM; 71 (46%) were focal, and 85 (54%) were diffuse type VM, and 97 (62%) were IA-VM. Of diffuse VM, 26 (31%) were Bockenheimer and 59 (69%) localized subtypes. Pure VM had a significantly elevated risk of IA-VM (RR 2.34 95% CI [1.42-3.89]). IA-VM was more common in diffuse (73%) versus focal (49%) types. Risk of IA-VM in diffuse type VM was significantly elevated (RR 1.48 95% CI [1.13-1.94]). 100% of genuine diffuse VM had IA-VM, this subtype had the highest risk (RR 1.83 95% CI [1.56-2.14]) of IA-VM. Limitations Retrospective, single institution study. Conclusion Intraarticular involvement of the knee should be considered in all lower extremity VM. Pure VM and the Bockenheimer diffuse VM subtype had the highest risk of IA-VM.