What could cause a TT amputee to experience external rotation of the heel at heel strike?

The phenomenon of external rotation of the heel at heel strike in a transtibial (TT) amputee can often be attributed to the characteristics of the prosthetic foot, particularly if the prosthetic heel is too firm. When the heel is excessively firm, it does not compress adequately upon load during heel strike, which can lead to the heel rotating externally as the body weight shifts onto the prosthesis. This external rotation can disrupt the otherwise desired alignment and stability of the prosthetic limb during the gait cycle, leading to abnormal gait patterns.

The interaction between a firm heel and the ground can create a lever effect that causes the foot to rotate outward. In a properly functioning prosthesis, the heel would provide sufficient cushioning upon impact, allowing for a smooth transition and maintaining a neutral foot position. Therefore, a prosthetic heel that is too firm is directly associated with the occurrence of external rotation at heel strike, making it the most relevant factor in this scenario.

Understanding how the heel's firmness impacts gait mechanics is crucial in prosthetic design and adjustment, highlighting the importance of ensuring that components are optimally designed to accommodate the specific needs of the amputee during ambulation.