The Four of Swords indicates a break from the routine, a pause, a desire to find peace of mind, a process of healing, of recuperation. The Knight of Cups is emotional, romantic, compassionate. He can be a helper or a mediator. In his negative manifestation, he can be emotionally unstable, unfaithful, obsessive and manipulative. Both cards are related to healing and recuperation, so it's very possible that when this combination appears, we'll have to deal with issues that revolve around matters of emotional or physical health.
The elements of the cards are Air (Four of Swords) and Water (Knight of Cups). The Air of the Four of Swords provides the necessary dose of logic, so that we don't get carried away by emotions and it gives this combination a rather reserved tone. The two cards can work well together, especially if we manage to keep a relaxed and patient attitude