Running-related Achilles tendon injury: a prospective biomechanical study in recreational runners

Key Points

1. A more flexed knee at initial contact and at the midstance phase of running were significant predictors for developing Achilles tendon (AT) pain.
2. The results suggested that a 1-degree increase in knee flexion at initial contact and midstance was associated with a 15% increase in the risk of developing an AT injury.
3. This causes a limitation in training or stoppage in running.

BACKGROUND & OBJECTIVE

Achilles tendon (AT) pain occurs in 22% of running-related injuries. Overload is believed to be the cause with more dorsiflexion and eversion in the loading phase. Another associated issue is knee flexion. However, this demonstrates inconsistent results in cross sectional and retrospective studies and creates difficulty understanding if the biomechanics of the ankle and knee are the cause or the consequence. The literature lacks quality prospective studies to determine the factors associated with AT injury.

This study aimed to determine whether biomechanical variables were related to the incidence of AT pain for one year in low-volume runners.

Achilles tendon pain occurs in 22% of running-related injuries.

Strengthening the gluteus maximus and retraining it so a 10° forward lean is achieved, will bring the knee backwards, decreasing the external moment arm and the strain on the AT.

METHODS

The study included 108 runners. Participants who had a previous running injury or ran more than 51 km/week were excluded. Runners aged 18–65 years were included. Weekly data was collected over one year on injury incidence. A running-related AT injury was defined as pain in the AT region requiring medical evaluation or causing a stoppage or modification of running. The kinematics and kinetics of the overground running of the lower extremities were recorded. The lower-extremity joint angles were analyzed at initial contact and at midstance. The maximum values of joint angles in the sagittal plane were analyzed.

RESULTS

After the 1-year evaluation period was completed by 103 (95%) of the 108 participants, it was included in the analysis. 18 participants (17%) reported AT pain on both lower limbs; eight participants (8%) reported AT pain on the right lower limb only; and five participants (5%) reported AT pain on the left lower limb only during the 1-year evaluation period. A total of 37% males and 25% females with an average age of 35 years reported an AT injury. The biomechanical data indicated that runners with AT pain had significantly greater maximal ankle dorsiflexion during the stance phase, a more flexed knee at initial contact and greater maximal knee flexion at midstance. The results indicate that a more flexed knee at initial contact and midstance are significant predictors for developing AT injury (see figure 1).

LIMITATIONS

• AT injuries were not clinically diagnosed, instead a weekly questionnaire was used.

• The accumulation of exposure and injury occurrence were not accounted for.

• Only the right lower limb biomechanics were assessed.

• Another limitation is that they do not have a biomechanical analysis of running due to fatigue.

• They also only analyzed running biomechanics in standardized, laboratory neutral shoes. The footwear in which participants ran during the 1-year follow-up was not controlled.

• A final limitation is that they did not have information on whether participants’ running biomechanics may have changed during the 1-year follow-up.

CLINICAL IMPLICATIONS

The main purpose of the article was to determine the incidence of AT pain and its biomechanical risk factors. The authors observed a 30% incidence over a 1-year period and state their findings are higher than other studies (7-22%) (1-5). They feel it may be due to the inclusion of runners who ran on hilly conditions.

Participants who developed AT pain ran with more ankle dorsiflexion and knee flexion during stance phase. However, only knee flexion was a significant risk factor associated with the development of AT pain.

The authors explain that the increased knee flexion could be attributed to the gastroc length tension relationship. The force-generation capacities of the gastroc are greatest in full knee extension. This may mean that, if a runner goes into greater knee flexion and ankle dorsiflexion, the force–length relationship for the ability to generate maximum force at the gastroc becomes disadvantageous and, therefore, the soleus may take on a greater role for force generation.

There has been discussion in the past that the deeper fibers of the tendon are derived from the soleus and they are more often the problem in AT pain, especially regarding the insertional variety. This study would support that theory.

The authors note another main cause of the development of AT pain is the larger external moment arm at the knee (distance between the ground reaction force vector and the anteriorly located knee joint center) compared to runners who did not develop AT pain.

One aspect that was not mentioned in the study was trunk position. An upright trunk will demonstrate a knee strategy vs a forward trunk lean which demonstrates a hip strategy. Strengthening the gluteus maximus and retraining it so a 10° forward lean is achieved, will bring the knee backwards, decreasing the external moment arm and the strain on the AT.

+STUDY REFERENCE

Skypala J, Hamill J, Sebera M, Elavsky S, Monte A, Jandacka D (2023) Running-Related Achilles Tendon Injury: A Prospective Biomechanical Study in Recreational Runners. J Appl Biomech, 39(4), 237-245.

SUPPORTING REFERENCE

1. Hein T, Janssen P, Wagner-Fritz U, Haupt G, Grau S. Prospective analysis of intrinsic and extrinsic risk factors on the development of Achilles tendon pain in runners. Scand J Med Sci Sport. 2014;24(3): 201–212
2. Messier SP, Martin DF, Mihalko SL, et al. A 2-year prospective cohort study of overuse running injuries: The Runners and Injury Longitudinal Study (TRAILS). Am J Sports Med. 2018;46(9):2211– 2221
3. Kluitenberg B, van Middelkoop M, Smits DW, et al. The NLstart2run study: incidence and risk factors of running-related injuries in novice runners. Scand J Med Sci Sports.
4. Nielsen RØ, Rønnow L, Rasmussen S, Lind M. A prospective study on time to recovery in 254 injured novice runners. PLoS One. 2014;9(6)
5. Lagas IF, Fokkema T, Verhaar JAN, Bierma-Zeinstra SMA, van Middelkoop M, de Vos R-J. Incidence of Achilles tendinopathy and associated risk factors in recreational runners: a large prospective cohort study. J Sci Med Sport. 2020;23(5):448–452.