Bring water to a boil

Meanwhile heat the oil i a large skillet over medium high heat. Add the sausage and cook until lightly browned, about 4 minutes. Add the pine nuts, garlic, and crushed red pepper; cook, stirring frequently until the nuts are lightly browned and the sausage in dark brown, about 2 minutes.

Add the pasta to the boiling water and cook until al dente. Drain, reserving about 1/2 cup of the pasta water. Return pasta to the saucepan; add the sausage mixture, spinach, and the reserved water; toss to coat.