One type of toe walking is also called "habitual" or "idiopathic" toe walking, where the cause is unknown.[2] Other causes include a congenital short Achilles tendon, muscle spasticity (especially as associated with cerebral palsy) and paralytic muscle disease such as Duchenne muscular dystrophy.[3] A congenital shortening of the Achilles tendon can be hereditary, can take place over time as the result of abnormal foot structure which shortens the tendon, or can shorten over time if its full length is not being used. Toe walking is sometimes caused by a bone block located at the ankle which prevents the antagonist movement, dorsiflexion. This cause is often associated with trauma or arthritis.[4] It may also be one way of accommodating a separate condition, foot drop.