Step 1: The goal of a fasciotomy is to release the trapped pressure inside a muscle compartment, which is walled in by the unyielding deep fascia.
Step 2: Because the deep fascia is the structure causing the constriction, decompression is impossible unless that layer itself is divided.
Step 3: Reaching it requires cutting through everything above it in order - skin, subcutaneous tissue, superficial fascia - and then through the deep fascia.
Step 4: So all four layers down to and including the deep fascia are incised, making the answer skin + subcutaneous tissue + superficial fascia + deep fascia.
\[\boxed{\text{Skin + subcutaneous tissue + superficial fascia + deep fascia}}\]