Extensor expansion

Bands

• lateral bands pass on either side of the proximal phalanx and stretch all the way to the distal phalanx. The lumbricals of the hand, extensor indicis muscle, dorsal interossei of the hand, and palmar interossei insert on these bands.
• A single median band passes down the middle of the finger along the back of the proximal phalanx, inserting into the base of the middle phalanx.
• A band known as the retinacular ligament runs obliquely along the middle phalanx, and connects the fibrous digital sheath on the anterior side of the phalanges to the extensor expansion.