Prosthetic alignment is important for walking function and walking comfort in people with a transtibial amputation (TTA). Prosthetic alignment is defined as the position of prosthetic parts relative to the body and to each other. A suboptimal alignment decreases stability and increases energy use during walking. Therefore, finding the optimal alignment is an important aspect of rehabilitation. Shoe heel height is considered to influence prosthetic alignment, walking comfort and gait symmetry in people with a TTA. Unfortunately, research on the effect of heel height is scarce and no evidence is available on the effects of variations smaller than 20 mm. However, these small heel height variations between store-bought shoes are often overlooked by people with an amputation and may cause secondary musculoskeletal problems in the long term. To increase the knowledge on this topic, this study aims to examine the effects of small increases in heel height on gait symmetry in people with a TTA and healthy individuals. It was expected that higher heel height would cause more asymmetry in gait and lower walking comfort. People with a TTA were expected to be affected more by heel height changes than healthy individuals.

Optimal prosthetic alignment is essential to achieve a functional gait pattern in people with a transtibial amputation (TTA). A suboptimal alignment decreases stability, increases the metabolic costs of walking, and increases the risk of secondary musculoskeletal and stump problems. Prosthetic alignment is defined as the position of the prosthetic parts relative to the body and to each other. Dynamic alignment of the prosthesis, especially the 'fine tuning' of the prosthesis based on the patient's needs, is a continuous process during rehabilitation.

Throughout the entire alignment process the prosthetists takes the shoe heel height of the patient into account. Moreover, patients are advised to search for a similar heel height when purchasing new shoes. However, prosthetic walkers frequently report complaints during their follow-up visits with their prosthetist or rehabilitation physician that possibly are related to prosthetic misalignment. Although several studies describe the effects of heel height on gait in healthy individuals, our knowledge about the effects of heel height within the TTA population is still limited to one study examining heel height changes of 20 millimeter. The variation in heel height of commercially available shoes is often smaller, and therefore easily overlooked by people with a TTA. Since it is not clear what the effects of smaller heel height variations on the gait pattern are, additional research is needed to enable prosthetists and therapists to better advise their patients.

Therefore, the primary objective was to examine the effect of small increases in heel height on gait symmetry in people with a TTA. It was expected that a larger increase in heel height would result in more gait asymmetry and lower walking comfort. In addition, healthy individuals were included in whom smaller effects of the heel height changes were expected.

Inclusion Criteria:

• had their prosthesis for at least one year (participants with a TTA)

Exclusion Criteria:

• (other) neurological or orthopaedic impairments affecting walking ability
• surgery on the lower extremities within the last six months
• the use of a walking aid