This is a series on low back pain. If you missed the summary of causes, go back to Part 1.
Running all the way down your back are two sets of muscles, together called the erector spinae. They keep the spine erect. With the prevalence of postural issues at all age levels, these muscles are common causes of low back pain. The longissimus is nearest to the spine and the iliocostalis farther out on the ribs. They merge in the lumbar spine with the longissimus muscle fibers ending there (tendinous fibers continue to the sacrum) and the iliocostalis muscle fibers terminating on the sacrum with their tendons. They can work together in a unit or separately on parts of the spine a little like a snake.
Their action when working together is to straighten the spine and extend it backward. When working only on one side they do side bending (lateral flexion) and some rotation. They function as stabilizers, resisting gravity as you bend forward and sideward. (This is called a lengthening contraction.) At 90 degrees of forward flexion they are in maximum activity and the ligaments have been active since 45 degrees. For those of you in pain, note that coughing and straining with constipation causes vigorous activity of the erectors. Interestingly, when you are standing perfectly straight on your feet, your back completely relaxes! Another plug for good posture.
The Trigger Points from the erector spinae that refer to the low back come from the lower segments. Pain is referred mostly into the buttock all the way from the top of the hip bone to the bottom crease.
Dysfunction in these postural muscles can cause joint dysfunction at the level where they are tight. Pressure in the joint fires off the nerves which produces pain. Functional (not structural) curves in the spine can cause contraction of the muscles on the convex side.
Conversely, scoliosis from genetic sources or from structural asymmetries is a huge factor in producing pain by contracting the back muscles unevenly. A longer leg or bigger hip bone usually contracts the muscles on that side.
Chronic muscle contraction (tension or tightness) can lead to the formation of Trigger Points. Active and latent Trigger Points can create satellite and secondary Trigger Points in their referral zones. See the progression … pain that feels like it’s spreading. Rather, it’s like a relay race. One TrP passes signals to another zone which in turn passes the signals on to the next zone. In healing these conditions, one of them called Myofascial Pain Syndrome, the last in the relay line is the easiest to correct. The first or originator of the pain will be most resistant to healing and take the longest time.
As a Neuromuscular Therapist working in Metro West Boston, I treat these muscles every day. The gluteus maximus and medius are related, directly across the hip bone from the erector spinae and directly connected by the lumbosacral fascia. That’s the next post.