Tesla Patents Detail Optimus Hand and Knee Designs

Two newly published patents provide a detailed view of how Tesla is engineering its Optimus humanoid robot, emphasizing biomimetic mechanisms, efficiency, and inventive cable routing to tackle difficult robotics challenges.

Examining the hand and knee mechanisms clarifies how the system is being designed to be capable, durable, and energy-efficient.

The Hand: Eradicating Crosstalk

A high-functioning humanoid hand needs multiple tension cables acting as artificial tendons, routed from actuators in the forearm, through a highly mobile wrist, and into each finger.

A frequent problem, known as crosstalk, appears when wrist motion unintentionally tugs internal cables, making the fingers twitch or close without a command.

To address this, engineers Megan Giacobetti, Rod Jafari, Michael Leddy, Harry Edward Olive, and Shitong Pang describe an orthogonal cable transition placed at the wrist joint. On the forearm side, the control cables are arranged in a lateral, horizontal stack.

This layout shortens the leverage arm around the pitch axis (up–down motion). As the cables pass through the wrist’s rotational center, they transition into a vertical stack, which in turn reduces the leverage arm about the yaw axis (side-to-side motion).

The key benefit is that total cable length is preserved during articulation. By placing the tension cables at the rotational centers of both the pitch and yaw axes, the wrist can rotate freely without unintentionally tightening the finger tendons.

This isolates wrist and finger motions, helping avoid clumsy grasps and accidental drops, and it reduces computational overhead that would otherwise be used to counteract unintended finger twitches.

Beyond wrist routing, the fingers are built for durability and precision. Most fingers comprise four members: a distal tip, two middle members, and a base member.

Instead of simple pin hinges that wear and add friction, the finger members use curved contact surfaces that roll smoothly as the finger bends.

Each standard finger is actuated by three cables. One primary cable runs behind the base joint and in front of the upper joints to produce the main grasping motion.

The other two cables attach to the middle members to drive adduction and abduction, letting the robot spread its fingers side to side. Precision-machined internal channels keep these cables laterally aligned to their termination points, preventing crossing and fraying.

Iterative Improvements

According to Elon Musk on 19 April 2026, this patented hand design has already been modified and iterated.

We already changed the design. This one didn’t actually work.

— Elon Musk (@elonmusk) April 19, 2026

Elon indicated that the rolling finger joint did not work in practice. Whether a new hand-related patent appears or changes show up with the launch of Optimus V3 remains to be seen.

The Knee: Extreme Mechanical Leverage

Where the hand emphasizes low-friction routing, the robotic knee patent authored by Rod Jafari focuses on maximizing mechanical leverage and actuator efficiency, borrowing heavily from human anatomy to support walking, crouching, and lifting.

Rather than a conventional hinge, the knee employs a four-node mechanical linkage, a direct mechanical analog to the interactions among the kneecap, femur, tibia, and cruciate ligaments.

The four-bar geometry distributes dynamic loads across multiple nodes when, for example, the robot bends to pick up a heavy box, preserving joint integrity and preventing failure under heavy weight.

The knee is driven by a single linear actuator—effectively a precise servo motor—in the upper thigh. Owing to the linkage geometry, the actuator only needs to rotate its primary link member by about 60 degrees, which yields a roughly 150-degree rotational range for the lower leg.

This large motion gain is advantageous for a battery-powered humanoid: a small actuator displacement can generate a wide swing of the lower leg, cutting electrical power use while keeping the assembly compact.

To safeguard this highly leveraged system, a force sensor in the secondary link member measures real-time load on the leg. Processing circuitry then computes the exact micro-displacement the actuator must produce, taking into account the current leg angle, desired walking speed, and the torque required for the next step.

While Tesla was initially set to unveil Optimus in Q1, it now plans to do so closer to production to reduce the chance of competitors copying its work.