While technological development provides convenience, it has also caused permanent harm to some groups of people. Currently, commercial prosthetic limbs are mostly custom-made, making them expensive and hardly accessible. Therefore, BROFIX has developed leg prosthetics that can be 3D printed in multiple modes. They are designed according to standard human proportions, compatible with various fixing methods such as pneumatic support, springs, and rubber bands, and can be scaled up or down to size, as well as have adjustable weight. The modular design allows ordinary household 3D printers to print them. Technology benefits special groups, allowing everyone to walk and run with ease.

The leg prosthesis is designed in segments comprising four main components: the prosthesis socket, prosthesis thigh, prosthesis knee, prosthesis shin, and prosthesis foot, which can be printed at home using a 400*300*300 printer. 

The prosthesis thigh has three types of sidewall ring holes for the prosthesis socket. These dense sidewall ring holes on the thigh can match the sidewall ring holes of the prosthesis socket. Inside the prosthesis socket, skin-friendly cotton pads or silicone pads can be placed and fixed with stitching. This ensures a close fit with the skin while maintaining breathability, preventing skin abrasion from the stitches. 

The smaller sloped curvature of the upper arc wall of the prosthesis thigh ensures easy assembly and a snug fit, while the upper spherical wall distributes pressure evenly at the limb end. The central through-hole in the prosthesis thigh allows the removal of auxiliary sleeves or cloth pieces from the prosthesis socket when disassembling the leg prosthesis. 

The narrow design of the thigh's limit ribs allows them to fit tightly into the central groove of the prosthesis knee during stair climbing, preventing lateral wobbling that could cause misalignment and falls. The thigh limit ribs also feature through-holes in the socket limit ribs for installing gas supports. The thigh connection and fixation through-holes, and those connecting the thigh to the knee, allow fixed attachment while permitting limited axial rotation. The lower spherical surface of the thigh matches the spherical wall inside the knee cavity, ensuring minimal wear under heavy weight. 

The central fixing hole of the knee and the central groove fixing hole in the knee cavity are used for adding rubber pads for buffering. The thigh sidewall ring holes allow the installation of multiple springs or rubber bands. Additional through-holes on the knee side groove walls and thigh limit ribs allow for gas support installation by the user. These combined structures ensure that the thigh's axial rotation is responsive, adjustable in tension, and requires no electricity. Damaged components such as rubber pads, springs, rubber bands, or gas supports can be replaced or installed as needed. 

The knee side also has non-slip grooves on top, a raised surface on top, and side protrusions to limit multiple springs or rubber bands, ensuring even force distribution. Several thigh sidewall connection holes align with the connection holes on the prosthesis shin, enabling secure attachment. The alignment of these holes allows the leg prosthesis to be quickly assembled with simple screws, offering multiple adjustable length options, which can be tailored according to the individual's height.

The prosthetic lower leg is designed with multiple sidewall connection and fixing holes that match the through-holes of multiple sets of concave sidewalls on the prosthetic knee joint, allowing for longitudinal connection between the prosthetic knee joint and the prosthetic lower leg. This ensures a firm connection without any longitudinal wobble. Additionally, multiple through-holes are designed on the limit ribs of the prosthetic lower leg sidewall to facilitate the installation of support struts or springs with the prosthetic foot through-holes. The multi-hole design allows for adjustable tension of the installed struts or springs, making it convenient for various activities such as climbing stairs, hiking, or running. Furthermore, the sidewall connection and fixing holes of the prosthetic lower leg match the connection through-hole sizes of the prosthetic foot, allowing screws to be installed for stable connection and fixation. The screws can be 3D printed or purchased in suitable specifications. 

The prosthetic foot adopts an anthropomorphic design, ensuring aesthetics when wearing sandals with socks. The foot features a ring-shaped protrusion at the heel and a circular heel wall to prevent shoes from shifting or slipping during movement. Multiple groups of through-holes on the sole allow shoelaces to pass through and tie the artificial foot, further securing the prosthetic foot to the shoe. Additionally, multiple fixing grooves are designed to partially limit the shoelaces, ensuring that when the prosthetic lower leg rotates, the sidewall limit ribs pressing on the shoelace do not shift, maintaining elastic stress similar to a rubber band or spring, providing a fixing function. 

Extra grooves in the heel of the prosthetic foot can accommodate padding, providing cushioning and protecting the overall structure of the prosthetic leg when shoes are not worn. Moreover, multiple sole grooves provide grip to prevent slipping when going barefoot. Fixing nut recesses on the sole are designed to hide the nuts used for installing support struts or metal springs, ensuring the sole remains level. 

The prosthetic leg is designed with flat-side structures for the prosthetic socket walls, the concave sidewalls of the knee joint, the sidewall limit ribs of the lower leg, and the sidewalls of the foot. Apart from vertical slice printing, horizontal slice printing can also be chosen based on wear during use, ensuring overall structural toughness so that it does not experience significant wear or breakage under substantial weight pressure, fully safeguarding personal safety. 

This project is open-source. Please evaluate the risks before use. If you find design defects or have suggestions, please provide feedback, and we will update and improve it as much as possible.