Part of effective diagnosing is understanding the basics of how joints, muscles, and nerves work. People with low back pain commonly think they “pulled” a muscle. They may have. I will allow that it is possible. However, in ten years of work, not once have I diagnosed someone with a pulled or strained muscle (or tendon) in his low back. (It’s almost always a joint-driven problem - and joints can refer pain to muscles.)
A symptomatic pulled (also known as strained or torn) muscle - anywhere in the body - will hurt when contracted. Each personal case is different, but at some angle and with some type of resistance, when that disrupted muscle is asked to contract, it will provoke pain. The second finding with pulled muscles is that they often hurt when put on tension (stretch). This may or may not create a minimal range of motion loss in the plane in which the muscle is on tension. Third, when the affected muscle is on slack (at rest) and not contracting, nothing should happen and range of motion should be full.
An extensor muscle performs extension. If it is pulled you’ll usually find painful resisted extension, pain at end range of flexion with minimal to no motion loss, and full pain-free passive extension. This applies to extensor muscles everywhere, including in the low back. Therefore, if passive low back extension (prone, using the arms or a machine) is limited or painful, I’m not likely dealing with a muscle problem. If standing extension is pain-free but limited, I’m also likely not dealing with a muscle problem.
Again, knowing the foundations of biomechanics is essential. Just that simple piece of information can allow me to rule out a muscle. Unfortunately, many people (including clinicians) don’t apply these fundamental rules to diagnosing problems. Muscles can hurt due to referred pain, so just because pain is felt in a muscle doesn’t mean the muscle is the problem. A competent diagnostic process will provide the answer. -- Laura
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