An article of footwear includes an upper and a sole assembly. The sole assembly includes a unitary, open-celled structure. Specifically, the sole assembly includes a lattice structure having an interconnected network of struts and nodes that cooperate to define voids. The struts and nodes are configured to generate predetermined support and flexure properties within the network. The lattice may be configured as a conformal lattice, being contoured to receive accessories or complementary support structures. The sole assembly may further include an insert formed of compression material (e.g., foam). In operation, the lattice and foam insert cooperate to provide stability and cushioning to the article of footwear.