Background: The peroneus tertius is absent in 5% to 17% of the human white population. The function of the peroneus tertius is eversion and dorsiflexion of the foot. These 2 strength parameters have been identified as important parameters in the development of ankle ligament injuries.
Hypothesis: Subjects without the peroneus tertius are at higher risk for ankle ligament injuries.
Study design: Cohort study (Prevalence); Level of evidence, 1.
Methods: One hundred physical education students were palpated for the presence of peroneus tertius before the start of their education; they were also isokinetically measured for eversion and dorsiflexion strength. All ankle injuries were registered during 2 years, and exposure to sport was recorded.
Results: The peroneus tertius was absent in 37 of the 200 subjects (18.5%). In the group with peroneus tertius (n = 163), 21 ankle sprains (12.9%) were observed during the 2-year follow-up. In the group without peroneus tertius (n = 37), 7 ankle sprains (18.9%) were noted. Statistical analysis (Cox regression) showed no significant difference between both groups in the incidence of ankle sprains (P = .335). Comparisons between the group of subjects with peroneus tertius and the group without peroneus tertius concerning the concentric and eccentric isokinetic eversion and the concentric dorsiflexion strength did not attain significance at any tested velocity (P > .05).
Conclusion: This study shows that subjects without peroneus tertius are not at higher risk for an ankle ligament injury. In addition, subjects without peroneus tertius do not exhibit decreased eversion or dorsiflexion strength.
Clinical relevance: This study is the first to clarify the exact contribution of the peroneus tertius within the muscular system around the ankle. As a result, the clinical importance of the peroneus tertius concerning prevention and treatment of ankle ligament injuries is low.