Here are the answers to all 9 questions:

In extensor substitution (seen in pes cavus), the extensor muscles overcompensate for limited ankle dorsiflexion and a tight gastroc-soleus complex. The cavus foot makes initial contact laterally and loads the forefoot early — the extensor substitution pattern is most notable during the loading/forefoot loading phase as the extensor tendons are recruited excessively to achieve ground clearance and compensate for equinus.

HAV disrupts normal first ray function and reduces the windlass mechanism, impairing the propulsive phase of gait. The result is an apropulsive gait — the patient cannot generate adequate push-off through the first MTPJ and instead abducts the foot to offload it.

AAFD (posterior tibial tendon dysfunction) results in a collapsed medial arch and hindfoot valgus. Appropriate interventions include: medial heel skive, rearfoot varus posting, deep heel cup, and increased medial arch profile to support the collapsed arch. An increased lateral arch profile would further load the lateral column, worsening the valgus collapse — this is contraindicated.

The Manchester Scale (Garrow et al., 2001) is the established visual grading system for hallux valgus severity. It uses a standardised set of photographs and classifies deformity into four levels: no deformity, mild, moderate, and severe. It has excellent interobserver reliability (kappa = 0.86).

Posterior ankle OA causes pain at end-range plantarflexion/dorsiflexion contact posteriorly. A full-length heel raise reduces dorsiflexion demand throughout the entire stance phase, offloading the posterior ankle joint. A short heel raise alone would create a rocker effect and increase forefoot loading without uniformly reducing ankle dorsiflexion stress through the whole foot contact.

In functional hallux limitus, the first metatarsal elevates under load due to a hypermobile or unstable first ray. The peroneus longus is the primary plantarflexor of the first metatarsal — its weakness (or functional ineffectiveness) allows the first ray to elevate, jamming the first MTPJ and blocking hallux dorsiflexion during propulsion.

The Footstool (Step Stool) Edge Test, described by Stainsby, assesses reverse windlass function. The patient stands with the MTPJs at the edge of a stool with toes hanging freely. Normal reverse windlass causes the proximal phalanges to plantarflex. Failure to plantarflex indicates plantar plate dysfunction or rupture.

Sagittal plane blockade (insufficient sagittal plane motion/compensation) produces signs related to excessive forefoot pressure and extensor overload: hyperextension of the distal phalanges (claw toes), callus sub 2nd/3rd MTPJs, callus under the hallux, and dorsal orientation of the hallux toenail. A callus under the styloid process of the 5th metatarsal indicates lateral column overload, which is a frontal/transverse plane issue (lateral instability, supination) — not sagittal plane blockade.

The metatarsal dome (metatarsal pad/dome) is the most commonly used orthotic accommodation for Morton's Neuroma. Placed just proximal to the metatarsal heads, it spreads the metatarsals, reduces compression of the interdigital nerve, and offloads the neuroma site. While an intermetatarsal plug is more specific, the metatarsal dome is the most widely used standard accommodation.