In the week after monthly options expiration (OPEX), SPY often “unclenches” into larger moves. The mechanism: the pinning gamma that had been damping volatility rolls off at expiration, removing a stabilizing force — and the market, no longer pinned, is freer to trend or swing. The post-OPEX unclench is a recurring, tradeable pattern in the market's monthly rhythm.
The mechanism
Going into a big monthly expiration, large concentrations of open interest create dealer hedging flows that tend to damp volatility — in positive gamma, dealers buy dips and sell rips, pinning price near heavy strikes. When that open interest expires, the associated hedging vanishes. With the pinning gamma gone, the market loses a source of stabilization, so moves that would have been damped can now run — hence the “unclench” into larger ranges the following week.
Why it recurs
This is a structural, monthly phenomenon tied to the expiration calendar, not a one-off. The build-up of expiring positioning creates the pin; its removal creates the release. The effect is often most pronounced after the large quarterly quad-witching expirations, where the most gamma rolls off. It's part of why the days right after monthly OPEX can feel more volatile and directional than the pinned days before it.
The market holds its breath into expiration and exhales after. The pin that kept it still rolls off — and the week after is where the delayed move often shows up.
Trading it
Anticipate the shift: as monthly OPEX passes, expect the pinning influence to fade and be more open to trending, larger-range moves in the following days. A market that was stuck in a tight, pinned range may break out once the expiration gamma clears. Watch the live gamma regime for confirmation that the damping has lifted. NoVo maps the live gamma and levels, so you can see when the pinning structure has rolled off and the tape has room to move.