Muscular causes of abnormal function

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Muscular causes of abnormal function

Weakness of inversion strength has been shown not to be associated with a pronated foot – a weakness in plantarflexion strength was found. Basmajian et al (1963) showed that the muscles did not play a role in the support of the medial longitudinal arch. Gray (? year) showed that the leg muscles are more active in those with flat feet.

Tibialis posterior:
• Most powerful supinatory of foot
• Weakness  excessive pronation of foot
• Tendon can slip out from behind medial malleolus  inefficient supinator – observe tendon during gait
• May be an abnormal insertion of tendon due to anatomical variation of navicular tuberosity and its accessory bone (if present)
• posterior tibial dysfunction  progressive pronated/flat foot.

Soleus weakness:
• Cannot stabilise cuboid on ground  peroneus longus prematurely transfers weight to medial side of foot

Peroneus longus weakness:
• Unable to stabilise first ray

Muscle spasm:
• Peroneus brevis  peroneal spastic flatfoot
• Peroneus longus  plantarflexed first ray
• Tibialis anterior  functions like a forefoot varus (ground reaction can overcome tibialis anterior as it has a short lever arm to STJ)

Role of intrinsic muscles:
• weakness of intrinsic muscle considered by some to be responsible for a ‘fallen arch’ or a pronated foot and exercise have been prescribed as a treatment

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