The multifidi are important proprioceptive sentinels for the low back, as well as the rest of the body, for virtually every activity you do weight bearing, including gait. They are implicated in many instances of low back pain, especially folks with flexion or extension intolerance, since their fiber orientation and thus mechanical advantage (or disadvantage) is dependent upon whether or not you are maintaining a normal lumbar lordosis.

Modalities which boost their function are an excellent adjunct to the rehabilitation process. Since they are not under volitional control (go ahead, try and contract your L2/L3 multifidus), they are innervated by the vestibulospinal tract and we must use proprioceptive work to engage them. Dry Needling is one modality that can help them to become functional again.

RESULTS and CONCLUSION:
“Significant difference was found in the percentage of change of muscle activation post needling between groups on the right side at level L4-5. A slight increase in the percentage of muscle activity, post procedure was observed in the dry needling group compared with the control group, although not significant in other segments examined. An improvement of back muscle function following dry needling procedure in healthy individuals was found. This implies that dry needling might stimulate motor nerve fibers and as such increase muscle activity.”(1). 

If you already needle this, as you may if you are needling the PPD's/segmental levels for the muscle you are needling (like L5-S1 for the glutes), great; if not, what are you waiting for?

What types of tests do YOU use to assess multifidus function? How about the multifidus lift test? The test looks at timing of contration of the multifidus; it should contract prior to the engagement of the appendicular muscles.

• Put the person in a quadruped position
• palpate the multifidus paraspianlly
• have the patient extend one leg
• the multifidus on the opposite side should contract prior to the extending leg

This test holds a lot of water and has been shown in the research to be effective (2).

"Our results provide preliminary evidence supporting the reliability and validity of the MLT to assess lumbar multifidus function at the L4-L5 spinal level." 

one variation that is more functional, in that the person is upright can be seen here:

And here is another variation while seated

“The clinical test of thoracolumbar dissociation was devised into assess a patient’s ability to perform anterior/posterior pelvic tilt in sitting while attempting to maintain a constant position of the thoracolumbar junction.

The results demonstrate that the clinical test of thoracolumbar dissociation has acceptable inter-rater reliability when used by trained physiotherapists. This test described here is the first to assess the ability to dissociate movement of the lumbopelvic region from that of the thoracolumbar region.” (3)

Here is a variation of the test that I use commonly in the office:

So, there you have it. Now get out there and needle!

1. J Back Musculoskelet Rehabil. 2015 Sep 6. [Epub ahead of print]
The immediate effect of dry needling on multifidus muscles’ function in healthy individuals. Dar G1,2, Hicks GE3.