The muscles from the front

The quadriceps muscles ('quads') dominate the front of the knee, and are the muscles making your 'lap'. If you sit down and put your hands on your lap, then spread your fingers open - all of that muscle under your fingers are the bulky quadriceps. The image on the left is not great but it shows that the patella exists within the substance of the quadriceps tendon, the fibrous bit at the bottom which attaches to the tibia (shin bone). The proper name for the quads is 'quadriceps femoris'. In the photo on the right the arrow is pointing to the vastus lateralis muscle (a part of the quads), bulging out at the side of the thigh.