Compartment syndrome (CS) occurs when the pressure in an enclosed compartment increases due to tissue swelling or internal bleeding. As the intra-compartmental pressure (ICP) builds up, the blood flow to the tissue or the organ is compromised, resulting in ischemia, necrosis and damage to the nerves and other tissues. At the present there are no established diagnostic procedures, and clinical observations such as pain, paralysis and even compartment pressure monitoring are an unreliable determinant of the presence of the syndrome. Late diagnosis may result in fasciotomy, neurological dysfunctions, amputation and even death. Focusing on the frequently occurring CS of the lower leg, this work is aimed toward introducing a coherent, mechanically motivated analysis of the disease within the framework of poroelasticity. The fascia enclosing the compartment is treated as an inextensible and impermeable layer, and the tissue inside the compartment is represented as a fully saturated poroelastic solid. The model quantitatively predicts the highly non-uniform ICP buildup as a function of both time and location. These findings, which are in good agreement with clinical observations reported in the literature, shed light on the difficulties associated with the identification of the syndrome and may assist in improved diagnostic procedures.