Background Chronic exertional compartment syndrome (CECS) is a common cause of exertional leg pain. It is commonly treated with a surgical fasciotomy, which has a surgical complication rate of up to 16% and takes approximately 6-12 weeks to return to preprocedure activity levels. Therefore, the development of a less invasive, effective outpatient intervention to treat CECS is desirable. Objective To describe and validate an ultrasound-guided (USG) fasciotomy technique for the anterior and lateral compartments of the lower limb in an unembalmed cadaveric model. Design Prospective, cadaveric laboratory investigation. Setting Academic institution procedural skills laboratory. Subjects Ten unembalmed cadaveric knee-ankle-foot specimens from 1 female (2 specimens) and 7 male donors aged 62-91 years (mean 78.6 years) with body mass indices of 18.9-35.3 kg/m2 (mean 27.1 kg/m2). Methods Two experienced operators each performed USG anterior and lateral compartment fasciotomies on 5 unembalmed cadaveric legs. A third physician subsequently dissected the legs to assess the continuity of the fasciotomies and to identify any neurovascular damage related to the procedures. Main Outcome Measures Fasciotomy length (in centimeters) and classification by completeness (achieved target length or did not achieve target length) and continuity (continuous or discontinuous) based on predetermined criteria. Muscles, retinaculae, and neurovascular structures were assessed for damage. Results No neurovascular injuries occurred in any of the 20 USG fasciotomies. The average fasciotomy length was 22.5 cm. All 20 of the fasciotomies achieved the target length. A continuous cephalocaudal fasciotomy was accomplished in 13 of 20 fasciotomies. When a fasciotomy was not continuous, the average length and number of intact fascial bands was 1.52 cm and 2.3, respectively. Conclusions USG fasciotomy of the anterior and lateral leg compartments can be safely performed in a cadaveric model and can achieve a fasciotomy length comparable to surgical fasciotomy. Most procedures successfully achieved a continuous cephalocaudal fasciotomy, although small areas of intact fascial bands were identified in approximately one-third of procedures. The clinical significance of this finding is indeterminate. Given the safety demonstrated with this minimally invasive USG fasciotomy in a cadaveric model, further research is warranted to develop and refine the technique for clinical application. Level of Evidence Not applicable.