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What is Hallux rigidus and explain in detail?
Hallux rigidus or stiff big toe is degenerative arthritis and stiffness due to bone spurs that affects the metatarsophalangeal joints (MTP) at the base of the hallux (big toe).
Hallux flexus was initially described by Davies-Colley  in 1887 as a plantar flexed posture of phalanx relative to the metatarsal head. About the same time, Cotterill first used the term hallux rigidus.

Signs and symptoms
Pain and stiffness in the joint at the base of the big toe during use (walking, standing, bending, etc.)
Difficulty with certain activities (running, squatting)
Swelling and inflammation around the jointAlthough the condition is degenerative, it can occur in patients who are relatively young, particularly active sports people who have at some time suffered trauma to the joint (turf toe). A notable example is NBA star Shaquille ONeal who returned to basketball after surgery.

Causes
This condition, which occurs in adolescents and adults, can be associated with previous trauma.
The true cause is not known. Most commonly, hallux rigidus is thought to be caused by wear and tear of the first metatarsophalangeal joint.

Classification
In 1988, Hattrup and Johnson described the following radiographic classification system:

Grade I – mild changes with maintained joint space and minimal spurring.
Grade II – moderate changes with narrowing of joint space, bony proliferation on the metatarsophalangeal head and phalanx and subchondral sclerosis or cyst.
Grade III – severe changes with significant joint space narrowing, extensive bony proliferation and loose bodies or a dorsal ossicle.

Treatment
Non-surgical
Early treatment for mild cases of hallux rigidus may include prescription foot orthotics, shoe modifications (such as a pad under the joint, and/or a deeper toe box to take the pressure off the toe and/or facilitate walking), specialized footwear (rocker-sole shoes), medications (anti-inflammatory drugs) or injection therapy (corticosteroids to reduce inflammation and pain). Physical therapy programs may be recommended, although there is very limited evidence that they provide benefit for reducing pain and improving function of the joint.

Surgical
The goal of surgery is to eliminate or reduce pain. There are several types of surgery for treatment of hallux rigidus