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Want more treatment options? Visit www.abmp.com to see Whitney Lowe's webinars, where he explores specific treatment approaches for common pathologies. which is the force used to produce a motion multiplied by the distance of that force from the axis of rotation. In essence, the closer a muscle is to the joint's axis of rotation, the less capable it is of producing significant force. The lumbar extensor muscles lie directly along the spine (very close to their axis of rotation) and are in a poor mechanical position for lifting activities, which can lead to muscle fatigue and injury (Image 1). The strong lumbodorsal fascia helps the lumbar muscles by lending tensile power from the other muscles connected to it, including the latissimus dorsi, gluteus maximus, transverse abdominis, and abdominal obliques. Their mechanical role is to produce tension on the lumbodorsal fascia, which then supports the lumbar muscles in lifting actions. Consequently, it is very important to address these other muscles when treating lumbar pain. Poor sitting postures and improper lifting techniques can produce radiating back pain. Long periods of isometric muscle contractions from sitting lead to chronic tightness, pain, and myofascial trigger points in the lumbar erector spinae muscle group. These chronic contractions, exacerbated by heavy lifting, can lead to facet joint dysfunction and disc pathology. FACET JOINT DYSFUNCTION The facet joints of the spine (zygapophysial joints), located on the posterior aspect of the vertebral arch, are the only bone-to-bone contact surface of adjacent vertebra (Image 2). Facet joint dysfunctions occur as a result of compression forces on the spine. When the disc loses height from compression, the facet joints compress together, irritating the adjacent contact surfaces of each vertebra. Even slight overloading of the back with the spine in extension can put excessive loads on the facet joints. Those with exaggerated lumbar lordosis have increased pressure on these joints. DISC PATHOLOGY Most disc herniations occur as a result of moderate compressive loads endured over time. Disc herniations develop in this worker population because of chronic compressive forces (sitting) and heavy lifting that places significant compressive loads on the discs, producing disc pathology. The disc is thicker on the anterior portion than the posterior in order to maintain the normal lordotic curvature of the spine (Image 3). When the spine is flexed, as it is during lifting activities, there is greater compression on the anterior aspect of the annulus fibrosis, while the posterior annulus is overstretched. The tensile forces on the posterior annulus, where it is overstretched, lead to weakening and eventual disc degeneration and herniation. KNEE BIOMECHANICS AND PATHOLOGY Delivery drivers also put an enormous demand on their knees. Constant bending of the leg with weight places adverse wear on the patella and its tendon, the anterior cruciate ligament (ACL), as well as the meniscus. Repetitive 3 Thicker disc on the anterior side. 3D anatomy images. Copyright Primal Pictures Ltd. www.primalpictures.com. Facet joints 2 Facet joints located on the posterior aspect of the vertebral column. 3D anatomy images. Copyright Primal Pictures Ltd. www.primalpictures.com. Disc is wider anteriorly www.abmp.com. See what benefits await you. 107