I wrote a little piece a few months earlier about Achilles tendonitis rehabilitation which focused on overloading the muscle and tendon eccentrically to change tissue characteristics. I wanted to add a little more about the kinematic motions of the lower leg that might add understanding of the abnormalities that may occur from or cause an Achilles tendon injury.
I came across an article that found individuals with a history of Achilles tendonitis exhibited a significantly lower peak knee internal rotation (tibia in relation to the femur) and no difference in tibial rotation motions (both groups showing about 13 degrees of tibial internal rotation) suggesting an increased relative internal rotation of the femur when compared to people without Achilles tendonitis. This increased internal rotation causes the lateral head of the gastrocnemius to move more anteriorly and the medial head to move more posteriorly. This shortens the medial head of the gastroc and leads to abnormal loading of the muscle and tendon. They also found the individuals with Achilles tendonitis showed a lower tibial external rotation moment and more ground reaction force through the lateral aspect of the foot. This suggests that they are avoiding the eccentric loading of the weak muscles that prevent internal rotation of the tibia during loading in stance (predominantly the posterior tibialis). They also noticed an abnormal increase in internal rotation of the tibia just after heel strike and just prior to toe off during gait. The researchers suggest that clinicians focus on strengthening patients in the transverse plane (specifically external rotation) as well as the sagittal plane to improve and prevent Achilles tendonitis.
(Click the link below for access to the article)
Study: Retrospective Cohort Study
Purpose: To determine if individuals with a history of Achilles tendonitis demonstrate a difference in transverse plane motion and moments at the knee and lower leg/tibia when compared to previously uninjured controls. And also to compare the synchrony of these events at the knee and lower leg between groups.
Subjects: They compared 8 individuals with a history of Achilles tendonitis in the experimental group to 8 individuals without a history in the control group. Individuals in the experimental group had at least 1 episode of Achilles tendonitis, all subjects were rearfoot runners, were asymptomatic at the time of the study, and ran a minimum of 6 miles per week for the past 3 months.
Results: The researchers found that individuals in the Achilles tendonitis group had significantly less peak knee internal rotation motion and tibial external rotation moment.
Limitations: There were three limitations that the researchers suggested. It is unknown if the biomechanical deviations were present prior to the development of Achilles tendonitis making it difficulty to determine if there is a cause and effect. Some variables did not reach significance because the power analysis showed a need for 15 more subjects to reach a level of significance. Finally, some subjects had other previous injuries that were not evaluated during this study that may have an effect on their biomechanics.