This study identified which residual-limb quality factors are related to functional mobility 1 year after transtibial (TT) amputation. A group of 28 TT amputees were evaluated with respect to their functional mobility (Prosthesis Evaluation Questionnaire [PEQ], Locomotor Index, Timed Up and Go test). The general (Chakrabarty score) and bony (tibial length, relative fibular length) residual-limb quality factors were assessed. An increase in general residual-limb quality (Chakrabarty >60) was correlated with greater functional mobility in one of the outcome measures (PEQ). For bony residual-limb quality, a tibial length of 12-15 cm distal from the knee joint line was correlated with greater functional outcome for all three outcome measures and the relative fibular length was not correlated with functional mobility for any of the outcome measures. This study showed that specific aspects of residual-limb quality are related to increased functional mobility. The amputation technique and resulting residual-limb factors may be important for patients to achieve functional prosthetic use.