This illustration looks a bit complicated at first, but if you identify the bones of the femur, tibia and patella it will become easier. The bones are shown from the side. The tissue spaces and folds within the knee joint are shown.
The lubricated spaces (eg the deep and superficial infrapatellar bursae) of the anterior interval are important for the smooth motion of the knee, as they allow the tissue planes to slide freely over one another. These spaces may become scarred during the abnormal healing process known as arthrofibrosis, rendering the knee stiff - and surgery to relieve this is called 'anterior interval release'.