HookEvent("player_hurt", Hurt);

public Action:Hurt(Handle:event, const String:name[], bool:dontBroadcast)  
{  
     new attacker = GetClientOfUserId(GetEventInt(event, "attacker"));  
     new client = GetClientOfUserId(GetEventInt(event, "userid"));  
         
     new String:WpName[25];     
     GetEventString(event, "weapon", WpName, 25);  
         
       if (StrEqual("knife",  WpName))  
       {  
          // Если ножом.
       }  
}