Stump sock

Stump socks are tubular medical or clothing accessories with a blind end that are fashioned similar to socks, usually without a heel. They are worn on amputation stumps for a number of reasons. As stump socks are typically worn on body parts that do not contain a foot, their definition is distinct from the average sock type garment.

Amputation stumps can be sensitive to cold or heat, particularly as their capacity to regulate tissue congestion is limited. The skin of amputation stumps can be very sensitive to allergic, chemical or mechanical irritation and thus may have to be protected.

There are different types of stump socks, some of which are available individually made to fit, some as industrially manufactured items:

...
Wikipedia