Throughout history, prosthetics have been painstakingly developed as a necessity for amputees, as human society has progressed to supplement what is missing and enhance what is weak.
The earliest recorded use of prosthetics is by the Greek historian Herodotlis: Hegistatu, a Belgian soldier captured in 848 BC, amputated his lower limbs when he was sentenced to death. Later, he was fitted with wooden prosthetics and became active again as an allegorist. You can see prosthetics from the 15th century in some historical museums in Europe. Prosthetics were made by weapon makers who made armor, so they were made of iron. It was only in the 17th century that wood was used to make the prosthetic socket of prosthetics and metal was used to make the knee joint, which making a great leap forward in prosthetics. This method was introduced to the United States in 1839, and naturally became the parent of the development of American wooden prosthetics. Harger, a Civil War casualty, learned from his own experience by placing rubber cushions on his ankles, the prototype of today's rear buffer.
About 69,000 people of Germany's World War I war wounded became amputees, and the social rehabilitation of these people spurred the development of the German prosthetic industry. After world War II, the prosthesis industry in the United States, the Soviet Union and Japan developed greatly, and institutions such as prosthesis research institute, prosthesis factory and vocational counseling center were established one after another. With the development of industry, various modern prostheses have been successfully developed by using alloy, plastic and other new materials. In addition, with the development of material science and engineering, the basic theories of artificial limb anatomical fit and dynamic and static alignment have been put forward under the inspiration of human biomechanics, which has made great progress in prosthetics as a subject.
   
Our country prosthesis foundation is weak. Before liberation, in Shanghai, Beijing and other big cities, there were prosthesis assembly rooms opened by Britain and the United States. In northeast China, there were prosthesis workshops opened by Japanese. In a few other cities, there were small workshops opened by private individuals. At this time, the prosthesis is mainly made of leather and aluminum, which belongs to the traditional prosthesis and has poor function. In liberation war period, the people's government in order to adapt to the needs of the disabled soldier, successively established prosthetic factory in north China, northeast China, east China liberated areas, the first public prosthetic factory established by the shanxi-chahaer-hebei border region government in zhangjiakou in 1945. After the liberation, especially after 1958, establish a factory prosthesis around the country, initially formed the assembly net prosthesis.
With the return of the investigation group to the Soviet Union in 1959, training courses were held, which conveyed the theory of the Soviet prosthetic assembly and promoted the physiological understanding of the prosthetic assembly. On this basis, in 1964, the Ministry of the Interior organized a unified design of the prosthesis, which was ready for standard production. In the 1970s, new changes appeared in China's prosthetic industry, and many new products were put into use. Such as hydraulic leg, nylon skeleton leg prosthesis, static ankle prosthesis, skeletal prosthesis, etc., all show the new progress of prosthesis.  
After 1979, with the opening up to the outside world, many international advanced prosthesis structures and assembly processes were introduced, which made China's prosthesis industry have a new leap, manifested in the following aspects:
(I) Update of prosthesis structure and type:
1. Popularization and application of leg prosthesis bearing by patellar ligament;
2. Assembly of full-contact leg prosthesis;
3. Development of skeletal thigh prosthesis;
4. Successful development of polyurethane prosthetic feet.
(II) Improvement of prosthetic socket material technology
The prosthetic socket of traditional prosthesis is made of leather, aluminum plate, wood, etc., which is difficult to fit with the stump, and the appearance is not beautiful. In recent years, there are great breakthroughs in technology and materials. The scientific method of molding is generally adopted, and the vacuum molding process is adopted on the repaired plaster positive model, and the materials are acrylic resin or unsaturated polyester, reinforced with polyester fiber and glass fiber. Due to the application of this process and materials, advanced full contact prostheses can be made.
(III) Scientific prosthetic assembly tools
In recent years the introduction of west Germany bearing frame, dynamic alignment instrument, assembly instrument. Domestic also developed "thigh position selector", "lower limb alignment adjustment instrument" and so on. Under the guidance of advanced assembly theory, the scientific assembly of prosthesis has made a gratifying step by using special instruments.
(IV) Comprehensive rehabilitation:
Prosthetic assembly is only a part of the rehabilitation of amputees. In recent years, not only the theoretical understanding has been unified, but also many prosthetic manufacturing units have opened rehabilitation clinics, physiotherapy, physical therapy, functional training and other projects to match the prosthetic assembly. Each hospital has also set up the prosthesis orthopaedic department, which has pushed forward the comprehensive rehabilitation of amputees a big step, so that the function of prosthetics get better play. The inclusion of prosthetics in the category of comprehensive rehabilitation is a major change in the concept of prosthetics.
This paper is divided into three parts to describe the AK prosthesis, the first part simply write some basic knowledge related to the thigh prosthesis; The second part describes the working principle of thigh prosthesis. The third part describes the production method of thigh prosthesis, this paper focuses on the working principle and production steps of thigh prosthesis, so that people understand the knowledge of AK prosthesis better, and master some basic production methods.