The good news is that sophisticated knee surgery is pretty much routine these days. In a two-hour, four-minute operation at Bethesda Naval Medical Center, doctors drilled four tiny holes in the presidential patella, or kneecap, and reattached the torn tendon with strong surgical thread. They used only a local anesthetic, known as an epidural, to avoid triggering the provisions of the 25th Amendment, which requires a temporary transfer of power to the vice president whenever the president is incapacitated. Clinton was numb from the waist down but remained alert, his doctors said, even helping to pick which CDs–Lyle Lovett and Jimmy Buffett–were played during the operation. In a briefing Saturday, White House spokesman Mike McCurry said Clinton was taking two non-narcotic pain relievers, Toradol and Ultran, and a muscle relaxant, Robaxin. White House officials said the president would rely on non-narcotic medications during convalescence.

His chances for full recovery are excellent, but he will have to work hard. Physical therapy–stretching and flexing the knee–began 15 hours after surgery and will become a daily routine, probably in the second-floor private gym at the White House. The first goal will be to strengthen his left leg and upper body. Then he will start gradual ““weight-bearing touch-down exercises’’ targeted on his injured knee. Golf and jogging are out, probably for four to five months, but the White House pool is in–if Clinton, a reluctant swimmer, will use it. Weight control is a must. After ballooning to 235 in 1992, Clinton weighed in at a relatively svelte 216 pounds during the 1996 campaign; his therapists will doubtless insist that he stay trim to speed the rehab process. During his trip to Helsinki, Clinton will wear a flexible ““range motion’’ brace to support his injured knee. The accident, while serious, is unlikely to be disabling. But it is a painful reminder that even a sitting president must watch his step.