An orthosis including an ankle joint device comprising an ankle joint body ; a first attachment member pivotally connected to the joint body, for pivotal movement about a generally horizontal axis in a dorsiflexion direction and a plantarflexion direction opposite to the dorsiflexion direction; a plantarflexion resistance spring configured to bias the first attachment member in a dorsiflexion direction relative to the ankle joint body when the first attachment member is within a plantarflexion resistance spring active angular range, the plantarflexion resistance spring active angular range beginning at a plantarflexion resistance spring recruitment angle and increasing in plantarflexion therefrom; and a dorsiflexion resistance spring configured to bias the first attachment member in a plantarflexion direction relative to the joint body when the first attachment member is within a dorsiflexion resistance spring active angular range, the dorsiflexion resistance spring active angular range beginning at a dorsiflexion resistance spring recruitment angle and increasing in dorsiflexion therefrom; a second attachment member connected to the ankle joint body about a generally horizontal axis; wherein one of the first attachment member and the second attachment member is configured for attachment to a lower leg of a human wearer of the device, and the other is being configured for attachment to a foot of a human wearer of the device characterised in that the second attachment member is pivotally connected to the ankle joint body and the orthosis includes further a second attachment member locking mechanism operable to lock the second attachment member at a selected angle relative to the ankle joint body. an ankle joint device comprising an ankle joint body ; a first attachment member pivotally connected to the joint body, for pivotal movement about a generally horizontal axis in a dorsiflexion direction and a plantarflexion direction opposite to the dorsiflexion direction; a plantarflexion resistance spring configured to bias the first attachment member in a dorsiflexion direction relative to the ankle joint body when the first attachment member is within a plantarflexion resistance spring active angular range, the plantarflexion resistance spring active angular range beginning at a plantarflexion resistance spring recruitment angle and increasing in plantarflexion therefrom; and a dorsiflexion resistance spring configured to bias the first attachment member in a plantarflexion direction relative to the joint body when the first attachment member is within a dorsiflexion resistance spring active angular range, the dorsiflexion resistance spring active angular range beginning at a dorsiflexion resistance spring recruitment angle and increasing in dorsiflexion therefrom; a second attachment member connected to the ankle joint body about a generally horizontal axis; wherein one of the first attachment member and the second attachment member is configured for attachment to a lower leg of a human wearer of the device, and the other is being configured for attachment to a foot of a human wearer of the device characterised in that the second attachment member is pivotally connected to the ankle joint body and the orthosis includes further a second attachment member locking mechanism operable to lock the second attachment member at a selected angle relative to the ankle joint body. <EOS>