The Crural interosseous membrane re-visited: Part II, new biomechanical concepts

Objectives Demonstrate movement of the Interosseous Membrane (IM) when tensile loading is applied to the Tibialis Anterior (TA) and Tibialis Posterior (TP). Postulate new roles for IM in running. Methods 9 IMs were assessed by 2 examiners. Dissections exposed the TA and TP. 1. Posterior IM was palpated under TP as tensile loading of TA applied. 2. Anterior IM was palpated under TA, as tensile loading of TP applied. 3. Tensile loading was measured via a spring scale attached to distal tendons of TA and TP. Results TA tensile loading caused movement of IM anteriorly. TP tensile loading caused movement of IM posteriorly. T-test revealed no statistically significant difference between two examiners. Conclusions The IM moves when TA and TP muscles undergo tensile loading. Rapid TA contraction during running pulls on the IM, pre-stretching TP and resulting in a forceful TP contraction. The IM is an important factor in pre-stretching of TA and TP. Nerve endings found in IM in our previous publication can increase afferent signal input and coordinate muscle activation of anterior and posterior IM muscles; IM acts as both a tendon and ligament; IM can coordinate muscular activity at heel strike and toe-off; IM limits separation of the distal tibio-fibular joint at heel strike; IM attenuates vertical ground reaction forces.