Option traders have been buying to open puts over calls on CarMax, Inc (NYSE:KMX - 32.20) in recent months. During the past 50 sessions, traders at the International Securities Exchange (ISE), Chicago Board Options Exchange (CBOE), and NASDAQ OMX PHLX (PHLX) have bought to open 3.71 puts for every call. Plus, this ratio ranks in the 95th percentile of its annual range, suggesting bearish bets have been picked up over bullish at a near annual-high clip.

This trend is being continued in today's session, with puts trading at nearly 13 times their average daily pace. Approximately 4,560 put contracts have crossed the tape so far, compared to fewer than 350 call contracts.

The September 30 put has garnered notable attention from short-term bears. Nearly three-quarters of the 1,500 contracts traded here have crossed at the ask price, and volume is outstripping open interest, allowing us to assume that new positions are being bought. In the best-case scenario, KMX will finish the week (when the options expire) below $29.51 (the strike price minus the volume-weighted average price of $0.49), representing a 9% slide from KMX's current price.

On a technical basis, KMX has been on a roller-coaster ride throughout 2012, and is currently sitting about 5% higher on the year. In recent months, though, the stock has been in a steady uptrend, carried higher by its 10- and 20-day moving averages. In fact, the stock has rallied nearly 30% since hitting its year-to-date low of $24.83 on June 28.

Given this recent run up the charts, as well as CarMax's impending turn in the earnings confessional, this buy-to-open put activity may simply represent shareholders protecting profits in case of a potential pullback. The stock dropped 7.8% after its fiscal first-quarter profit fell short of expectations. The company will reveal its second-quarter results before the market opens this Thursday. Wall Street is calling for a per-share profit of 52 cents.