Tibialis posterior in health and disease: a review of structure and function with specific reference to electromyographic studies

Abstract

Tibialis posterior has a vital role during gait as the primary dynamic stabiliser of the medial longitudinal arch; however, the muscle and tendon are prone to dysfunction with several conditions. We present an overview of tibialis posterior muscle and tendon anatomy with images from cadaveric work on fresh frozen limbs and a review of current evidence that define normal and abnormal tibialis posterior muscle activation during gait. A video is available that demonstrates ultrasound guided intra-muscular insertion techniques for tibialis posterior electromyography.Current electromyography literature indicates tibialis posterior intensity and timing during walking is variable in healthy adults and has a disease-specific activation profile among different pathologies. Flat-arched foot posture and tibialis posterior tendon dysfunction are associated with greater tibialis posterior muscle activity during stance phase, compared to normal or healthy participants, respectively. Cerebral palsy is associated with four potentially abnormal profiles during the entire gait cycle; however it is unclear how these profiles are defined as these studies lack control groups that characterise electromyographic activity from developmentally normal children. Intervention studies show antipronation taping to significantly decrease tibialis posterior muscle activation during walking compared to barefoot, although this research is based on only four participants. However, other interventions such as foot orthoses and footwear do not appear to systematically effect muscle activation during walking or running, respectively. This review highlights deficits in current evidence and provides suggestions for the future research agenda.

Figure 1

Cross sectional anatomy. Cross section of cadaver limb, taken 10 cm distal to the knee joint, indicating origin and depth of the TP muscle and inaccessibility for surface EMG investigation; tibia (T), fibula (F), tibialis posterior (TP) and neurovascular bundle (NV).

Figure 2

Gross anatomy of retromalleolar region. Gross anatomy of retromalleolar region indicating flexor digitorum longus tendon (FDL), tibialis posterior tendon (TP), medial malleolus (M) and tendo Achilles (TA). Small arrow indicates rounded TP tendon proximally and large arrow indicates the flattened area of tendon in retromalleolar region.

Figure 3

Audit of placement of intramuscular electrode. Gross anatomy of dissected limb with intramuscular electrode inserted, indicating; flexor digitorum longus muscle/tendon (FDL), tibialis posterior tendon (TP) and medial malleolus (M). Large arrow indicates wire electrode protruding from limb (3a and 3b) and small arrow indicates wire electrode passing through the muscle belly of flexor digitorum longus and into tibialis posterior (3b) with white paper to highlight electrode.

Figure 4

Tibialis posterior EMG activity during walking in health and disease. Tibialis posterior EMG activity during walking in health and disease – schematic estimates for ensemble-averaged tracings adapted from the respective studies. 0% and 100% represents heel contact to ipsilateral heel contact. Vertical lines show average timing of temporal gait events. Time resolution is approximated from original work to show a single gait cycle during walking. Amplitude characteristic are not scaled and cannot be compared among different studies. Linear envelopes for figure D-G show estimated unfiltered/unrectified signals. NB. Where multiple studies are available for each category, representation was based on the most recent work with the largest sample size.