I am not entirely sure whether I understand your question correctly. By asking about the "knights of unfortunate conditions," are you refering to the other knights that the knight who tells us about his experience with the lady dreams about? These figures are seen by the knight as he falls asleep with his lady, and obviously there appearance foreshadows the impact that his love for the lady will have on him and also gives the reader an important warning about the dangers of being taken in and deceived by a femme fatale figure. Note how these figures are described in the poem:
I saw pale kings, and princes too,
Pale warriors, death-pale were they all:
They cried--"La Belle Dame sans Merci
Hath thee in thrall!"
I saw their starved lips in the gloam
With horrid warning gaped wide,
And I awoke, and found me here
On the cold hill side.
Note the way that these figures are described as being "pale" and "death-pale," which should make us think of the way that the knight of the poem is described in the first stanza as "Alone and palely loitering." Not too the way that "their starved lips" are pictured as another sign of the distraction that they suffer. They are so focussed on love that it appears they have little appetite and are slowly wasting away. In spite of this timely warning, the knight has become yet another victim to La Belle Dame Sans Merci, and is suffering in the same way as a result from the sickness of unrequited love, as so many men have done before him.