How to make an IK rig in Blender: inverse kinematics for a leg or an arm, step by step

An IK rig lets you place a foot or a hand and have Blender bend the leg or the arm to reach it. This guide builds one by hand on a leg, with an IK control and a pole target, then covers the arm, Auto IK, Rigify and the usual errors. Menu names are those of Blender 5.2.

IK vs FK in Blender

With forward kinematics (FK), you pose a chain from its root to its tip: the thigh, then the shin, then the foot. Each child bone inherits its parent's rotation, so, as the manual notes, precise changes get harder the farther you go down the chain.

Inverse kinematics (IK) works the other way round. You position the end of the chain and Blender rotates the bones above it. A foot planted on the floor or a hand on a table becomes much easier to animate, while FK still suits an arm swinging freely. Blender IK mostly comes from bone constraints; Auto IK, covered below, uses the same method with fewer options.

What a simple IK leg needs

• Three deforming bones in a connected chain: thigh.L, shin.L and foot.L.
• An IK control, foot_ik.L: the bone the animator moves.
• A pole bone, knee_pole.L, in front of the knee: it decides where the knee points.

The names are examples, but keep a side suffix such as .L: Blender relies on it to mirror bones. Creating the armature and binding the mesh are covered in the Blender rigging guide.

Step 1: build the leg in Edit Mode

1. In Object Mode, press Shift+A and choose Armature (Single Bone in its submenu if Rigify is enabled), then press Tab for Edit Mode.
2. Place the head of the bone at the hip and its tail at the knee: this is the thigh.
3. Select the tail and press E to extrude the shin down to the ankle, then E again for the foot. Each extruded bone is a connected child of the previous one.
4. Name each bone in the Bone Properties tab, or by double-clicking it in the Outliner.

Then select the joint between the thigh and the shin and move it slightly forward with G. The IK solver starts from the current pose of the chain, here the rest pose, so this small bend tells it which way the knee folds. The Rigify manual asks for the same bend at knees and elbows, so that Rigify knows where they point.

Step 2: add the IK control and the pole

1. Select foot.L, press Shift+D, then Esc so the copy stays in place. Rename it foot_ik.L: its head sits on the ankle.
2. The copy is still parented to the shin. Press Alt+P and choose Clear Parent, or the control would move with the leg it drives.
3. Select foot.L, then foot_ik.L last, press Ctrl+P and choose Keep Offset. The foot now follows the control and takes its rotation.
4. Press Shift+A to add a single bone at the 3D cursor. Name it knee_pole.L and move it in front of the knee, at knee height, well away from the leg.

Step 3: turn off Deform on the control bones

Every new bone has Deform enabled, and foot_ik.L and knee_pole.L should never deform the mesh. Select each one, open the Bone Properties tab and untick the checkbox in the header of the Deform panel. According to the manual, this mutes the bone and also leaves it out of the weight calculation when you bind the mesh with Ctrl+P, With Automatic Weights.

Step 4: add the Inverse Kinematics constraint

Press Ctrl+Tab, choose Pose Mode in the pie menu, and select shin.L, the last bone of the chain that bends. Open the Bone Constraint Properties tab, click Add Bone Constraint and pick Inverse Kinematics in the Tracking column. Then set:

• Target: the armature object itself, then foot_ik.L in the Bone field that appears. The chain aims at the head of that bone.
• Pole Target: the armature again, then knee_pole.L. The manual describes the pole as what sets the roll of the chain, in other words where the knee or elbow points.
• Pole Angle: shown once a Pole Target is set. It turns the chain around the line from its first bone to the target.
• Chain Length: 2, for the shin and the thigh. It counts bones from the one that owns the constraint. A new constraint starts at 0, which means every ancestor up to the root.
• Use Tail: leave it on, the default, so the ankle is what reaches the target.

Move foot_ik.L with G: the leg follows and the knee bends toward the pole. Move knee_pole.L sideways and the knee turns with it.

A shortcut: select foot_ik.L, Shift+click shin.L to make it active, and press Shift+I (Pose > Inverse Kinematics > Add IK to Bone). Target Selected Bone adds the constraint with the control as Target; the pole and the Chain Length are still yours to set.

Fixing a leg that twists: Pole Angle

If the leg turns as soon as you set the Pole Target, and the knee no longer faces the pole, the cause is in Blender's source code. With Pole Angle at 0, the solver points the local X axis of the first bone, the thigh, toward the pole. That axis depends on the bone's roll and is not always the direction the knee bends.

Change Pole Angle, from -180 to 180 degrees, until the knee faces the pole again. When the knee bends along one of the thigh's own axes, the answer is a multiple of 90 degrees, so try 90, -90 and 180 first. Mismatched rolls along the chain can be aligned in Edit Mode with Armature > Bone Roll > Recalculate Roll (Shift+N).

The same IK chain on an arm

An arm uses the same setup with upper_arm.L, forearm.L and hand.L: a slight backward bend at the elbow in Edit Mode, the hand parented to its control, the constraint on forearm.L with a Chain Length of 2, and the pole behind the elbow.

For the other side, select the .L bones in Edit Mode and use Armature > Symmetrize. It creates the .R bones and, according to the manual, adjusts bone and constraint properties to mirror their behavior. Check both sides in Pose Mode.

Auto IK: quick posing without a constraint

In Pose Mode, open the Sidebar (N), Tool tab, Pose Options, and enable Auto IK. Moving a bone with G now rotates its parent, the parent's parent and so on to follow it. The chain only extends through connected bones, as far as they go by default; while moving, PageUp and PageDown, or the mouse wheel, change its length by one bone. With no pole and nothing to configure, the manual presents it as a limited feature for quick posing. The Pose Mode guide covers the rest of posing.

Rigify: IK and FK limbs generated for you

Rigify, an add-on that ships with Blender, generates limbs with both IK and FK controls. Enable it in Preferences, Add-ons, then:

1. In Object Mode, press Shift+A, Armature, and pick a meta-rig such as Human, or Basic Human, which has no face or fingers.
2. Fit the bones to the character, with knees and elbows slightly bent.
3. In Object Mode, click Generate Rig at the bottom of the Armature tab.

When a bone of the generated rig is active, the Item tab of the Sidebar shows a Rig Main Properties panel: a slider blends between full IK at 0 and full FK at 1, and buttons snap one set of controls onto the other. Rigify does not bind the mesh; its deforming bones are in the DEF bone collection.

Common IK mistakes

• The knee swings around as the control moves. The solver places the knee relative to the line from the base of the chain to the target, and the result becomes unstable when the pole gets close to that line. Keep the pole well in front of the knee.
• The whole body bends to reach the control. Chain Length is still 0, so the chain runs up to the root. Set it to 2.
• Bones stretch. Stretch, on by default, only scales bones whose IK Stretch value (Bone Properties tab, Inverse Kinematics panel, in Pose Mode) is above 0. Set it back to 0, or turn Stretch off.
• The knee bends backward. The leg was straight in Edit Mode, or the pole sits behind it.
• A constraint placed after IK seems ignored. IK constraints always run after the other constraints on the bones they affect, whatever their place in the stack.

What next

IK legs keep the feet on the ground while the body moves, the basis of the walk cycle guide. If the mesh pinches at the knee, the rigging guide shows how to fix the weights in Weight Paint mode.