Validation of a weight bearing ankle equinus value in older adults with diabetes

Accurate measurement of ankle joint dorsiflexion is clinically important as a restriction has been linked to many foot and ankle pathologies, as well as increased ulcer risk and delayed ulcer healing in people with diabetes. Use of the reliable weight bearing (WB) Lunge test is limited as normal and restricted ranges for WB ankle joint dorsiflexion are not identified. Additionally the extent of WB dorsiflexion restriction that results in clinically adverse outcomes is unclear. Therefore the aim of this investigation is to validate a proposed weight bearing equinus value (dorsiflexion < 30°) in unimpaired cohorts, and secondly to investigate any clinical effects this degree of ankle dorsiflexion restriction has on forefoot plantar pressure variables in older adults with diabetes.

Ankle dorsiflexion was measured using a Lunge test with the knee extended in young adults without diabetes (YA) and older adults with diabetes (DA). In-shoe and barefoot plantar pressure was recorded for the DA group. Spearman's correlation was calculated to determine any association between the presence of ankle equinus and plantar pressure variables in the DA group. DA group differences in people with and without an equinus were examined.

A weight bearing equinus of < 30°, assessed in a lunge using an inclinometer placed on the anterior tibia, falls within the restricted range in young unimpaired cohorts. In the DA group this degree of ankle restriction had a fair and significant association with elevated barefoot forefoot peak pressure (r = 0.274, p = 0.005) and pressure-time integrals (r = 0.321, p = .001). The DA equinus group had significantly higher barefoot peak pressure (mean kPa (SD): 787.1 (246.7) vs 652.0 (304.5), p = 0.025) and pressure-time integrals (mean kPa (SD): 97.8 (41.6) vs 80.4 (30.5), p = 0.017) than the DA non equinus group.

We support a preliminary weight bearing ankle equinus value of < 30°. This value represents a restricted range in young adults and is correlated with increased forefoot plantar pressure variables in older adults with diabetes. Mean population weight bearing ankle dorsiflexion data presented here for older adults with diabetes, will allow use of the more functional Lunge test with knee extended in research and clinical practice.