Ligaments on the Outside A Cable Brace That Copies the Knee's Own Wiring

This application covers a joint brace built around cables rather than rigid stops: a set of plates strapped to the leg, with a cable routed around them in loops that tighten exactly when the knee tries to move in a way that would tear a ligament. The applicant is Mobius Technologies, the American company behind the X8 knee brace worn in motocross and action sports, and the sole named inventor is its designer, Darren Fleming.

The Problem

The background section starts with the knee, which it calls a complex mechanism highly vulnerable to injury in sports like football, hockey, skiing, snowboarding and motocross. The two structures that fail most often are the anterior cruciate ligament and the medial collateral ligament, and the specification is careful to add that the wrist, ankle and elbow are at risk in many of the same activities for many of the same reasons, with wrist hyperextension singled out as painful and slow to heal.

The critique of existing braces is specific. A conventional ligament brace is a pair of rigid plates connected by hinges or straps, strapped tightly to the limb above and below the joint. The current state of the art in functional knee bracing, the document says, is a hinged framework fixed to the knee by adjustable straps. That arrangement is adequate for controlling lower pathology inducing loads, but it has not been shown to be effective at the clinically more important higher loads. In other words, the brace holds up fine until the moment that actually ruptures ligaments. What is needed, the specification concludes, is a design aimed at the mechanism of injury itself, without giving up comfort, fit, light weight and unobtrusive sports functionality.

What This Invention Does

Instead of relying on a hinge to block bad movement, the brace strings a cable around the joint the way the body strings its ligaments. The main claim describes a knee brace with a femoral plate on the thigh, a first tibial plate hinged to it, a second tibial plate below that, and a back plate behind the leg. A single cable starts at the femoral plate, runs down over the front of the tibial plates, around the back plate, up the other side, and crosses over itself at a point near the middle of the back plate before returning to the femoral plate. The routing is spelled out surface by surface in the claim, because the routing is the invention.

The result is what the specification calls control loops. As the leg moves through its range of motion and one loop extends, the opposite loop tightens, preventing the tibia from sliding forward into hyperextension, twisting into lateral rotation, or bending sideways relative to the femur. Those are precisely the motions that tear an ACL or MCL, and the cables resist them the way the natural ligaments do, progressively rather than with a hard stop. The tightening force of each loop is transferred toward the centre of the loop, which the document says increases the brace’s stability and effectiveness.

The claimed brace is also adjustable in an unusual axis. Two adjustment screws on the second tibial plate bear against surfaces on the first tibial plate and set an angle of rotation about an axis that passes through the wearer’s leg, letting the lower shell be rotated to match an individual’s alignment. Later figures extend the same cable logic to a wrist brace with an extension stop, and the specification notes that the cable systems can be retrofitted to conventional braces to increase their effectiveness.

Key Features

• Cables that behave like ligaments. The cable system acts much like the body’s natural ACL and MCL, resisting the forces that cause excessive joint movement rather than simply blocking motion at a hinge.
• Control loops around the joint. Two or more cable loops surround separate points near the joint, and as one loop extends the opposite loop tightens, giving precise control of hyperextension, lateral rotation and lateral bending.
• A routing that crosses itself. Claim 1 traces one continuous cable over the femoral plate, around the tibial plates and back plate, and through a cross-over point behind the knee, mirroring the crossed geometry of the cruciate ligaments.
• Screw-set rotational alignment. Two adjustment screws set the rotation of the lower tibial shell about an axis through the leg, so the brace can be tuned to the wearer’s anatomy.
• Not just knees. The drawings carry the same cable strategy to a wrist brace with an extension stop, with the ankle and elbow named as further candidates.
• Retrofit potential. The specification says the cable systems can be tailored or adapted to conventional braces, upgrading hinged designs already on the market.

Who Is Behind It

Mobius Technologies, LLC sells knee and wrist braces under the Mobius brand, best known for the X8 knee brace launched into the motocross world with multi-time AMA champion Ryan Villopoto as an early partner. The X8’s headline feature, a continuous cable routing system that externally reinforces the knee ligaments, is recognisably the technology described in this specification. Darren Fleming, the sole named inventor, is the engineer credited in industry coverage with designing the X8 after a string of his own knee injuries.

The priority chain is straightforward for once. This application is a divisional of Australian application 2020291528, the national phase of PCT/US2020/037078 filed on 10 June 2020, which claims priority from United States application 16/436,786 filed on 10 June 2019. The document also incorporates by reference a run of earlier US applications reaching back through 13/867,910 and 12/987,084 to 11/744,213, which points to a design lineage much older than the 2019 priority date.

Why It Matters

ACL injury is one of the most common serious sports injuries, with long recovery times, high reinjury rates and a well documented link to later osteoarthritis. Whether knee braces actually prevent these injuries has been debated for decades, and the specification’s own framing, that hinged braces control the low loads but not the high ones, is a fair summary of why. A brace that engages progressively along the same lines of action as the ligaments is a genuinely different mechanical answer to that criticism, and it is the answer Mobius has been selling to motocross riders for years.

The claim strategy is worth noting. Claim 1 does not claim cables on a brace in the abstract; it recites one specific routing, surface by surface, plus the screw-adjustable tibial shell. That is a narrow claim, but it reads closely onto a commercial product, which is often exactly what a small company wants from a divisional: a clean, defensible fence around the thing it actually ships. Filing it in Australia, a country with a large motocross and off-road riding market, and keeping the family alive through a divisional six years after the PCT, suggests the orthotics at the core of the brand are considered worth protecting for the long haul.

Related Concepts

• Anterior cruciate ligament – the knee ligament whose function the primary cable loop imitates.
• Medial collateral ligament – the second ligament the control loops are routed to protect.
• Anterior cruciate ligament injury – the injury the brace is designed to prevent or keep from recurring.
• Orthotics – the field of externally worn devices that support limbs and joints.
• Bowden cable – the general engineering principle of transmitting force along a routed flexible cable.
• Motocross – the sport in which the applicant’s cable braces are best known.

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AU 2026202111 was published in the Australian Official Journal of Patents on 9 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.