The tibialis posterior reflex
What is the Tibialis Posterior Reflex?
The tibialis-posterior reflex is one of the muscular reflexes. This means that the blow on the muscle's tendon triggers the response in the same muscle.
The posterior tibialis muscle is located in the lower leg. When the corresponding tibialis posterior tendon is hit - i.e. a reflex release - the edge of the foot on the inside lifts upwards. This is also called supination. The reflex is always checked in side-by-side comparison and the one-sided weakening can, for example, indicate a herniated disc. The interconnection of this reflex takes place in the spinal cord at the level of the vertebral bodies L5 and S1. These can be found in the lower back.
How do you test the tibialis posterior reflex?
Muscle reflexes are tested in that the examiner briefly hits the tendon of the muscle to be tested. For this, the muscles must be completely relaxed.
The patient's supine position is best suited for the tibialis-posterior reflex. The examiner lifts the knee slightly with his arm and briefly feels below or above the medial malleolus of the foot for the tibialis posterior tendon. The reflex is triggered and the inside of the foot is lifted (supination) by a short, rapid blow with the reflex hammer on the tendon. This test is always carried out in a side-by-side comparison, as the reflex strength is different for everyone and only a side difference can reliably indicate damage.
If the reflex strength is very low, the patient can clench their teeth firmly or cross their hands and pull them apart. This increases the reflex level and the examiner can better assess the reflexes. For a more detailed examination, the examiner can also place electrodes on the muscles and nerves and measure the time it takes for the body to transmit the reflex. However, this is only done for very specific questions or for scientific reasons.
To properly test this reflex, it is important to know the course of the tibialis tendon. Therefore, please also read our page: Tibialis posterior tendon
What does a weakening of the reflex indicate?
A reflex always runs through two nerve connections: from the muscle up into the spinal cord and then back to the muscle, where the muscle movement (contraction) is triggered. If there is damage to the reflex arc, the reflex becomes stronger or weaker, depending on the extent of the damage.
A weakened reflex is more likely to indicate a problem near the muscle. One-sided weakening is the most likely damage to the nerve. If this is the case on both sides, it is more a question of damage to the spinal cord in which the relex is interconnected.
For a better understanding, we recommend that you read more about the reflex arc, as this is where the interconnection of the reflexes takes place and damage leads to a weakening or strengthening of the reflex. You should therefore also read: Reflexes (the reflex arc)
What does a strengthening of the reflex indicate?
Although reflexes are interconnected via the spinal cord, they can be modulated by the brain.
When the reflex is triggered, the head says that it is not so strongly required and slows it down. A strengthening of the reflex thus indicates damage above the spinal cord segment L5 or even damage in the brain. In this case, the brain cannot transmit the weakening command and the reflex is triggered with maximum strength.
