Scaly leg is a disease of chickens and other birds. It is caused by a parasitic mite, Knemidocoptes mutans. The mite burrows under the scales in the bird's legs, but may also infest other areas, such as the comb or wattles of chickens. The mite spends its entire lifecycle on the birds and is usually spread by direct contact.

Birds infested with scaly leg have raised or protruding scales, sometimes with a white crusty appearance. Scaly leg is irritating to the infected bird, and in extreme cases can result in lameness.

In domestic birds the disease may be treated by application of an oily substance such as petroleum jelly, vegetable oil, or a commercial chest rub, thus preventing the mites breathing. Alternatively an insecticide may be used to kill the mites – or the two methods may be combined. The loose crusty scales may also be removed by soaking the afflicted bird's legs in soapy water mixed with diluted ammonia, and the encrusted areas |scrubbed gently with a soft brush. Complete removal may take multiple treatments. Dropped scales may remain infectious for up to a month, and so pen, perches, and nesting areas may also be treated, or birds may be moved to different housing for several weeks.

The Scaly-breasted Lorikeet (Trichoglossus chlorolepidotus) is an Australian lorikeet found in woodland in eastern Australia. The common name aptly describes this bird, which has yellow breast feathers broadly edged with green that look like scales.

The Scaly-breasted Lorikeet was first described by German zoologist Heinrich Kuhl in 1820. Other names this bird is known by include the Gold and Green Lorikeet, Greenie, Green Lorikeet, Green and Yellow Lorikeet, Green Keet, Green Parrot, Green Leek, Greenie, and Green Leaf. It is often colloquially referred to as a "Scaly". Its specific epithet is derived from the Ancient Greek root chloro- "green", and Latin lepidotus "scaly".

The Scaly-breasted Lorikeet is about 23 cm (9.0 in) long. The crown and sides of head are emerald-green slightly tinged with blue, while the feathers of the back of the neck and throat and breast are yellow, broadly edged with green, giving scaly appearance. The tail is green with the base of the outer tail-feathers marked with orange-red. The lower flanks, thighs and undertail-coverts green are strongly marked with yellow, while the underwing-coverts are orange-red. They have orange-red eyes, and their bills (beaks) are dark coral-red. Their legs are generally grey-brown.

A leg is a weight bearing and locomotive structure, usually having a columnar shape. During locomotion, legs function as "extensible struts" - the combination of movements at all joints can be modeled as a single, linear element capable of changing length and rotating about an omnidirectional "hip" joint.

As an anatomical animal structure it is used for locomotion. The distal end is often modified to distribute force (such as a foot). Most animals have an even number of legs.

As a component of furniture it is used for the economy of materials needed to provide the support for the useful surface, the table top or chair seat.

Many taxa are characterized by the number of legs:

In tetrapod anatomy, leg is used to refer to the entire limb. In human medicine its precise definition refers only to the segment between the knee and the ankle. This segment is also called the shank, and the front (anterior) of the segment is called the shin or pretibia.

In bipedal tetrapods, the two lower limbs are referred to as the "legs" and the two upper limbs as "arms" or "wings" as the case may be.