Rune diagnosis is a helpful tool for healers and spirit workers.
Prior knowledge of the divinatory meaning of the Runes can be useful but not a necessity for healing purposes.
Drawing a single Rune will give you a general idea of the issue or its source.
I personally prefer to draw 3 Runes: one for the physical aspect of the issue, another one for its psycho-emotional aspect and a last one for its spiritual aspect.
This will be fully covered in the Rune Healing home study course I am currently designing.