How did Beethoven expand the usual number of movements in sonatas?

While typical sonatas consist of two, three, or four movements, Ludwig van Beethoven particularly expanded the scheme to four movements during his earlier period.1

When a fourth movement was included in the Classical tradition, it often functioned as a simpler, dance-style movement—such as a minuet or a scherzo—placed between the slow second movement and the finale, though its placement could vary. Beethoven frequently chose to accelerate the traditional minuet into a scherzo, a quick and light movement that became a hallmark of his structural approach. In some extreme cases, such as in his ninth symphony, Beethoven expanded the binary structures of both the scherzo and the trio into complete sonata-form structures, further increasing the scale and complexity of his works.12