Chapter 4

BASIC CONCEPT: FUNCTIONAL INSTABILITY

Suppose a patient has 0 - 90 total degrees of knee flexion. The joint is hypomobile. How functionally stable is that joint in a squat position?

Suppose a patient has full flexion and extension of his knee joint. The anterior cruciate ligament has been torn and the tibia has excessive anterior glide. The joint is hypermobile. How functionally stable is that joint?

Neither the hypomobile joint nor the hypermobile joint exhibit stability in all aspects of function.

From a physical therapist’s point of view, neither the hypomobile nor the hypermobile spinal segment exhibit functional stability. It is understood that the hypomobile knee joint will require mobilization followed by muscular stabilization of the newly gained motion. The hypermobile knee joint will require muscular stabilization, bracing for specific activities, and in the most severe cases, surgical stabilization.

The physical therapist faces many of the same issues when dealing with a spinal segment. While both the hypomobile and the hypermobile segments are considered functionally instable to a physical therapist, treatment for each will take a different approach. The hypomobile segment may require mobilization followed by stabilization while the hypermobile segment will require stabilization without mobilization. Some spinal segments will need external bracing for added stability. Other segments may need surgical procedures in addition to the treatment offered by the physical therapist.

  Next: Chapter 5