Do injuries trigger formation of lipomas?

The cause of lipomas is not known. Some have suggested trauma but the idea is that the lipoma could occur in the area of the trauma, not in a distant area. 

Hello, thanks for your query. The post trauma lipoma is still controversial there has been studies where there have been lipomas developed after blunt trauma. Firstly, the formation of so-called post-traumatic 'pseudolipomas' may result from a prolapse of adipose tissue through fascia induced by direct impact. Alternatively, lipoma formation may be explained as a result of preadipocyte differentiation and proliferation mediated by cytokine release following soft tissue damage after blunt trauma and haematoma formation. But formation of lipoma at distant site  from trauma is hard to explain. 

It is uncertain what the root cause of lipomas are, however there are hereditary conditions that lead to patients having multiple lipomas throughout the body.  Luckily, lipomas in and of themselves are benign tumors that can be removed.  Best wishes.