Conservative treatments such as in-shoe orthotic heel wedges to treat musculoskeletal injuries are not new. However, weak evidence supporting their use in the management of Achilles tendonitis suggests the mechanism by which these heel wedges work remains poorly understood. It was the aim of this study to test the underlying hypothesis that heel wedges can reduce Achilles tendon load. A musculoskeletal modelling approach was used to quantify changes in lower limb mechanics when walking due to the introduction of 12mm orthotic heel wedges. 19 healthy volunteers walked on an inclinable walkway while optical motion, forceplate and plantar pressure data were recorded. Walking with heel wedges increased ankle dorsiflexion moments and reduced plantar flexion moments. This resulted in increased peak ankle dorsiflexor muscle forces during early stance and reduced Tibialis Posterior and toe flexor muscles forces during late stance. Heel wedges did not reduce overall Achilles tendon force during any walking condition, but did redistribute load from the medial to lateral triceps surae during inclined walking. These results add to the body of clinical evidence confirming that heel wedges do not reduce Achilles tendon load and our findings provide an explanation as to why this may be the case.