Thanks for your question. As you know the tibialis posterior muscle from the interosseous membrane, lateral part of the posterior surface of the tibia, and superior two-thirds of the medial surface of the fibula. It travels between the flexor digitorum longus and flexor hallucis longus to insert into the tuberosity of the navicular, cuneiforms, cuboid, and the bases of the 2-4th metatarsals.
The function of the tibialis posterior is one of ankle plantar flexion, calcaneal inversion and plantar flexion as well as stabilization (through compression) of the first ray complex (talus, medial cuneiform, navicular and base of the first metatarsal). It acts additionally to help decelerate subtalar pronation. Further stabilization of the midfoot comes from smaller tendon slips inserting onto the other cuneiforms, metatarsals, the cuboid and the peroneus longus tendon.
The more common problems that can occur with the tibialis posterior complex are those of muscular strain, tendonitis, tendon insufficiency (stretch) and partial or complete tears. Excessive or prolonged pronation causes excessive dorsiflexion of the distal first ray complex, increased pronatory effects, and as discussed above, dysfunction of the 1st MPJ joint. The dorsiflexed 1st toe will compromised the efficiency of the windlass mechanism which “winds up” the plantar fascia, properly positions the paired sesamoids, and thus limit effective dorsiflexion of the 1st MPJ. This dorsiflexion of the first ray requires the tibialis posterior to undergo excessive eccentric load for a longer period of time, thus placing more stress on the tendon and muscle belly.
Clinically we find that more people are flexor driven. Therefore we work quite a bit with increasing extensor function, thus a lot of our rehab protocals involve strengthing Anterior Tib as opposed to Posterior Tib. To this one must ask what is your criterior for strengthening the posterior tib, if over pronation or navicular drop has led you to this conclusion then you may want to reexamine the clinical findings for what muscles may actually be involved.
That being said, there times when it is clinically necessary to strengthen the Posterior Tibialis muscle and we like the following exercises
1. Single Leg Balance with Arch Supports:
Begin standing on one foot. Attempt to raise the medial longitudinal arch and hold in tact while maintaining the body stable over the foot.
2. Single Leg Balance with Arm Swings
Perform the exercise above and add to it multi planar arm swings while maintaining medial arch integrity and balance. Cross body arm swings that generate torso rotation, and simulated axe and pitching motion with each arm are effective motions to use.
3. Seated Forefoot Adduction and Inversion
This exercises utilizes some sort of resistive device such as a theraband that will wrap around the forefoot to attach somewhere lateral to the body creating lateral resistance. while stabilizing the ipsilateral knee with the contralateral hand the exercise is performed by adducting the forefoot against resistance towards the midline.
4. Inverted Calf raises
This exercise is performed standing. it should be started as a double support exercise and can be transitioned into a single support for added challenge. the exercise is performed by performing a standard calf raise with or with out Y-axis resistance and adding an inverted moment at the apex of the raise and then lowering back down.
5. Closed Chain Unilateral Supination
Standing on one leg on a step with the knee slightly flexed and the medial border of the foot over the edge of the step. Exercise is performed by lowering and lifting the arch from pronation to supination.
6. Now perform the sequence with appropriate arch intergrity WITHOUT the arch supports
These exercises should get you started. Good luck and let us know if you have any other questions.
The Gait Guys