It seems like the perpetrators and victims are often members of gangs and involved in drug dealing. Of course with some knife crime the victims are innocent but I suggest that is not the norm.
Why aren't gang members who've been knifed innocent victims? They are often attacked when out on their own or in a small group. Sometimes, living in a particular area and not being part of the local gang makes an individual a target, and the only way not to be a target is to become a member of the gang.
Unless its a knife fight I'd say any one stabbed is a victim irrespective of whether or not they are a gang member.