When Lower Extremity Dysfunction Contributes To Back Pain
If these factors are combined with a leg length discrepancy that is in play during movement, this will often shift the destabilized disc more unilaterally. Certainly, a unilateral sagittal plane dysfunction can also cause a back problem to be more one-sided. These situations all cause axial rotational torquing forces that ultimately create significant localized muscular overuse and ultimately disc damage. However, this discussion is beyond the scope of this article.
At the point of the aforementioned compensatory flexion, the hip extensors will fire in an attempt to stabilize the spine by trying to reverse the abnormal flexion. This attempt for muscular stabilization to stabilize the axial skeleton and intervertebral discs may result in muscular tightness or spasm, which is probably the first symptom that back pain patients will experience.3
Making this scenario more problematic is that the lower extremities in an adult account for approximately 15 to 20 percent of one’s total body weight.3 The lower extremities are primarily attached anteriorly to the L1-L4 vertebrae and their intervertebral discs via the iliopsoas muscle complex. When the low back and hip on the stance limb is in early flexion in the gait cycle, as a result of a sagittal plane blockage or disturbance, this negates the normal and effortless forward swing of that limb. This early flexion subsequently creates a need for the lower extremities to be lifted and carried forward, thereby demanding the assistance of the iliopsoas complex, creating a 15 to 20 percent body weight load on the destabilized low back.
Over time, this “repetitive motion” of lifting and moving this weight load on the low back yields injury to the unstable discs as I previously described. This torsional load also extends to the L4- L5 level due to the abnormal rotational forces and muscles involved when the hip flexes.
So what causes the early lumbar flexion that results in this repetitive damaging cycle?
A Closer Look At Sagittal Plane Pivots And Kinetic Chain Flexion
In an attempt to appreciate and accept this conceptually, one has to consider a broader and perhaps more simple understanding of what occurs during walking.
Dananberg has offered the scientific and research basis for this discussion in many peer-reviewed articles that thoroughly explore and explain these sagittal plane concepts in detail.4-10 Murphy has also been instrumental in teaching these and other contributing aspects relating to physical movement, demonstrating their biomechanical influences on damage in and about structures proximal to the foot.12-14
Essentially, one needs to appreciate that the foot should move through three distinct pivots in each individual gait cycle. The first pivot is rolling over the heel itself after heel strike. The second pivot is ankle dorsiflexion that causes the heel to lift off the ground and the final pivot is the movement over the MPJs with the hallux being passively stable on the weightbearing surface via the first MPJ flexor stabilizing mechanism. These are essentially the three pivots of the foot in one gait cycle, which enable the body to pass over the unobstructed passive stance limb.