Radial vs. Ulnar Deviation: What the Terms Actually Mean

Anatomically, the lead wrist's cocking motion during a golf swing is a combination of radial deviation (the wrist bending toward the thumb side) and, later in the swing, some ulnar deviation (bending toward the pinky side) as the club releases. Golf instruction usually collapses both into the single word "hinge," which is convenient shorthand but hides an important distinction when it comes to fitting equipment.

Radial Deviation: The Backswing Set

Radial deviation is the motion most golfers picture when they think of "cocking" the club — the lead wrist bending so the clubhead rises relative to the hands during the backswing. This is the motion primarily responsible for building the angle between the lead arm and the shaft that shows up on a hinge-angle readout.

Ulnar Deviation: The Release

Ulnar deviation happens later, largely through the downswing and into impact, as the wrist straightens back out and the clubhead works back toward being in line with the lead arm. This motion is what most golfers experience as "releasing" the club, and it's closely tied to when and how fast the stored angle from radial deviation gets used.

Radial deviation builds the angle on the way back. Ulnar deviation spends it on the way down. A fitting that only accounts for one half of that pair is only solving half the problem.

Why This Distinction Matters for Grip and Shaft Choice

A golfer who forms a large radial deviation angle but releases it (ulnar deviates) very quickly needs different support than a golfer who forms a smaller angle but holds it longer before releasing. The first golfer often benefits from a shaft that resists loading too early, giving the quick release more time to stay controlled. The second golfer often benefits from a grip taper that makes it easier to actively hold the angle a beat longer, since their formation style already has more built-in patience.

The Takeaway

Next time a fitting or lesson mentions "wrist hinge," it's worth asking which half of the motion is actually being measured or discussed. Formation (radial deviation) and release (ulnar deviation) respond to different equipment changes, and treating them as one motion tends to produce fittings that only address half of what's actually happening in your swing.