In the literature, 85% - 95% of all low back pain cases are non-specific. This literally means we don't have a reliable way of knowing where the exact problem is originating from.
Muscles, ligaments, discs, and facet joints in the lower back have overlapping pain referral patterns which adds another layer of difficulty in pin-pointing the nucleus of pain.
Often, healthcare providers will utilize the One Finger Test which is carried out by having the patient point to the site of their perceived pain. It is certainly helpful to acquire this information although this is not a reliable stand alone test to isolate the origin of lower back pain.
Two-point discrimination varies greatly by body part. The minimal distance of detecting two separate points of stimulus on your finger can range from 2-8 mm while the lower back can range between 40-70 mm! That is a big difference. If someone touches your back, with two fingers simultaneously a couple of inches apart, it will feel like like you are only being touched by one. Try it!
Why is this? Simply, the lower back doesn’t occupy as much sensory real estate in your brain. The sensory receptors at your lower back are less densely packed compared to other areas such as your fingers. As such, with the overlapping pain referral possibilities and the relatively poor sensory input, patients often find it challenging to describe the exact location of their discomfort. Therefore, as always, a thorough history and assessment is necessary if attempting to make the non-specific lower back pain more specific.