UE5 IK Not Working? Here’s How to Fix Inverse Kinematics
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UE5 IK Not Working? Here’s How to Fix Inverse Kinematics

So you’ve been working with Unreal Engine 5 and suddenly your inverse kinematics (IK) rig stops working. The character’s foot won’t touch the ground, or maybe the hands are floating in space. Don’t panic! IK can be tricky sometimes, but fixing it isn’t as scary as it sounds.

TL;DR

If your UE5 IK setup isn’t working, it’s likely due to missing bone references, animation blueprint errors, or misconfigured IK nodes. Check your retargeting settings and make sure your skeletal mesh supports the right bones. Use the IK Rig and IK Retargeter efficiently, and always test with real movement. IK in UE5 is powerful but needs careful setup.

What Is Inverse Kinematics (IK) Anyway?

In simple terms: inverse kinematics is the magic that makes characters move naturally. Instead of rotating each joint manually, IK lets you move one part—like a hand—and the rest of the arm follows.

This is great for:

  • Feet sticking to uneven terrain
  • Hands grabbing objects or walls
  • Characters looking natural in motion

Common Reasons Your IK Might Not Work

There are a few classic mistakes that can cause IK systems to fail in UE5. Before you get down into blueprint spaghetti, check these first!

1. You’re Missing a Proper Skeleton

IK systems rely on bones. If your mesh doesn’t have the right bones (like foot or hand joints), IK can’t function. Make sure you’re using a skeleton that supports full limb control.

2. IK Goals Aren’t Assigned

In the IK Rig or Control Rig, you need to assign goals. These are the target positions for your hands and feet. If they’re not set, nothing will move.

3. Your Animation Blueprint Isn’t Driving IK

The animation blueprint (ABP) needs to tell your IK rig what to do. If the IK nodes are missing or placed in the wrong part of the graph, they won’t execute.

4. Retargeting Issues

If you’re using retargeted animations (like from Mixamo or another skeleton), they might not carry over the IK data correctly without a proper IK Rig and Retargeter setup.

How to Fix UE5 IK Step-by-Step

Okay, you’ve spotted a problem. Let’s fix it! Follow these steps to get your IK working again.

Step 1: Check Your Skeleton

  • Open your skeletal mesh.
  • Look in the Skeleton Tree for key IK bones, like ik_foot_l, ik_foot_r, ik_hand_l, and ik_hand_r.
  • If they’re missing, you might need to add them—or use a different skeletal mesh with those bones.

Step 2: Build or Review Your IK Rig

  • In UE5, go to the Content Browser and right-click your skeletal mesh.
  • Choose Create IK Rig.
  • Add Solvers (like Full Body IK or Two Bone IK) and make sure bones are linked properly.
  • Assign IK Goals for hands and feet. These are target bones that control where limbs go.

Step 3: Set Up or Fix Your Animation Blueprint

The Anim Blueprint is where the IK logic should be applied after the base animation plays. Here’s the simple order you should follow in the AnimGraph:

  1. Play Base Pose (from an animation or state machine)
  2. Apply Control Rig or IK nodes

Make sure the IK doesn’t go before your base pose. You want to adjust the pose—like foot position—after the original animation has moved the character.

Step 4: Enable Bone Retargeting (If Needed)

Using someone else’s animations? Then IK won’t just work magically. Do this:

  • Create an IK Rig and a matching IK Retargeter
  • Set up goals in both rigs (source and target)
  • Match bone chains and verify alignment
  • Retarget animations with correct IK context

Step 5: Use Debug Tools

Still stumped? No worries. Try using:

  • ShowDebug Anim in-game
  • Pose Watch in the Anim Blueprint
  • UE’s Live Preview in the Control Rig

These tools will tell you if the IK goals are even receiving values. If they’re NULL or zero, your rig isn’t talking to the blueprint.

Bonus Tip: Blend It!

Let’s say your IK works, but it’s just too jerky or strong. You can blend from FK (forward kinematics) to IK smoothly.

Use blend nodes to drive your IK amounts:

Lerp(FK Pose, IK Pose, IK Alpha)

You can animate the IK Alpha over time to get gradual transitions. Instant pops just feel wrong, especially for feet.

When All Else Fails… Use Control Rig

UE5’s Control Rig is a powerful way to build custom IK logic. If solvers in the IK Rig don’t give you what you want, try building it from scratch.

You can create your own logic for limbs and define how bones respond to movement, game inputs, or even physics.

Checklist: IK Quick Fixes

Before you start over, run through this checklist:

  • ✔ Does your skeleton have IK bones?
  • ✔ Are Goals set in your IK Rig?
  • ✔ Is the animation blueprint applying IK after the base pose?
  • ✔ If using retargeted animations, is the IK Retargeter set up?
  • ✔ Have you used debug tools to view IK in real time?

Wrap Up

Inverse Kinematics in Unreal Engine 5 can be super powerful when it works. But when it doesn’t, it often just comes down to missing references, wrong node order, or a misconfigured rig.

Take it one step at a time.

And remember, even the pros get IK issues every now and then. The trick is to troubleshoot with a checklist and never be afraid to go back and reassign your goals.

Now go out there and get those limbs moving right!