A sock liner in a running shoe acts as a moisture barrier between the foot and the insole of the shoe, and provides light cushioning as well. Not all shoes have sock liners but those that do can provide a wealth of information for you and your patients. An easy way to educate patients about their foot function is to show them their sock liner wear patterns.
The image at left shows a pair of sock liners worn in shoes by a patient who developed Achilles tendonitis. Notice the asymmetrical wear? Walking and running gait analysis after the sock liner inspection identified excessive tibial varum on the right foot, consistent with an inverted heel strike and a laterally deviated, center of force trajectory during midstance. This resulted in an excessive (angled) pull on the Achilles leading to symptoms with the right foot. An orthotic incorporating inversion correction greater on the right foot than the left was able to address and balance this asymmetry.
This sock liner image at the right is from a runner who was experiencing posterior tibial tendonitis. The sock liner wear pattern is consistent with a medially deviated subtalar joint axis and elevated first ray, resulting in increased left hallux pressure. In this case, I prescribed custom orthoses to address the medial subtalar joint axis deviation with a Kirby skive and medial flange. I also ordered a reverse Morton’s extension to restore function to the first metatarsophalangeal joint.
If you are not evaluating your patients’ worn, removable sock liners, you may be missing valuable diagnostic information, which can guide you in your treatment approach.