In directional terms for the foot, the bottom surface is called the plantar surface. The term plantar comes from the sole of the foot, and it’s the standard label used for that underside, as in plantar fascia or plantar flexion. Dorsal refers to the top or dorsum of the foot, ventral is a front/belly-side term used more generally for the body, and anterior means toward the front. Since the question is about the bottom surface, plantar is the precise, widely used term.

Cryotherapy is the therapeutic use of cold to treat tissue injury and pain. Applying cold causes vasoconstriction, which limits swelling and inflammation, and it also slows nerve conduction to reduce pain. When liquid nitrogen is used, the temperature drop is extremely rapid and deep, allowing very targeted or widespread cooling for procedures like cryosurgery or quick reduction of inflammation in some injuries. This is distinct from thermotherapy, which uses heat to increase blood flow and tissue extensibility; hydrotherapy involves water at various temperatures as a medium for therapy; and massage is manual manipulation of soft tissues. So, the cold-focused approach described fits cryotherapy.

Inflammation of tendons that connect muscle to bone is tendinitis. In the ankle, tendons such as the Achilles can become irritated from overuse or injury, leading to pain, swelling, and difficulty with movement. This fits the description of a tendon inflammation in the ankle. Pes planus is flatfoot, not a tendon issue. Plantar fasciitis involves the plantar fascia (a band of tissue, not a tendon) and causes heel pain, not tendon inflammation. Excisional matrixectomy is a nail surgery, unrelated to tendons.

Restricted motion at the base joint of the big toe refers to limited range of motion at the first metatarsophalangeal joint, especially dorsiflexion during push-off. The best term for this is hallux limitus, which specifically describes a partial restriction in movement at that joint and can progress if the condition worsens. Hallux limitus reflects the early stage where motion is reduced but not completely lost, often due to cartilage wear or osteophyte formation. In contrast, hallux valgus is a bunion with lateral deviation of the big toe, a deformity rather than a ROM limitation. Hallux rigidus denotes a more advanced, near- or complete loss of motion at the same joint. Metatarsalgia refers to generalized pain under the ball of the foot, not limited to the big toe joint’s motion.