Pick up that skirt flapping below your knees a few inches and take a good look-those knees might be coming out of hiding again, if the Italian designers have their way. In the first round of the fall fashionmarathon, which has now moved through London into Paris, stores' buyersand press in Milan watched last week as skirts grazed the middle of theknee at many collections and actually hovered a bit above at some (Giorgio Armani and Basile among them). Many of the collections were still "retro" in a big way (take your pick-'20s through early '60s) with the suit still leading the pack from the broad-shouldered, shaped suit with slim skirt or a wider and shorter pant, to the dressier dinner or evening suit. The Fendi sisters (with the aid of Karl Lagerfeld) drew rave notices for a innovative presentation of shapes and colors in fur from the packed audience, thankful for something other than the uniformity they found in many of the collections.

Many buyers, who had already come to Milan with instructions to be cautious about ordering and to watch prices (already up 5 to 15 percent for fall), were calling the Italian offerings "uneven" and many of the clothes repetitious. But there were high marks for Tai and Rosita Missoni's collection of knitted belted jackets andtextured reversible coats, Giorgio Armani's drapped jackets and Krizia's shaped coats and toppers.

Now after a few days viewing London's offerings for fall, the fashion pack has moved on to Paris for their fall shows.

Nipped in waists, tight-fitting bodices, sequins and pearls sound familiar? They did to four members of the Corcoran Women's Committee whoposed for a reshot of a photo taken 22 years ago at the Corcoran Ball. Sidi Smith, Eleanor Lippitt, Sue Nelson and Betty Osgood (left to rightin both photos), who are all still members of the committee, selected gowns from Bloomingdale's for the photo but agreed that, looking back, their 1957 dressed aren't too far from what's likely to show up at this year's ball on April 20.

With all of the period shows on TV these days, you may be wondering where all the antique clothing is coming from. If some of the clothing in last week's PBS series "The Scarlet Letter" looked like it was dragged in the mud, splotched with grease and full of tea stains, it's because those are some of the techniques used by the costume designers to make th outfits look genuinely old. Costume designer Franne Lee didn't want to use new fabrics for the clothing and so she concentrated on old lace doilies, tablecloths and whatever antique fabric she could find for the 145 costumes in the production. When she had to resort to using a modern fabric, she had it washed about 15 times to achieve an old look.

It's true confessions month in the current McCall's. You think you've got problems-poor Cheryl Tiegs says that her lips are too thin and she has to work very hard at keeping her so-called natural beauty. Her make-up artist Rick Gilette says, "We use pale shades of lipstick which look very soft and make her lips look fuller. We avoid harsh lines and dark colrs, which tend to minimize the mouth." Gaptoothed Lauren Hutton also keeps Gilette in business. "I use alternating light and dark shading to straighten her nose. I shade the left and lighten the right sides of her jaw. I overline the right upper and left lower parts of her lips to fill them out."

Sick of displaying designer's all over your body? This may be the best form of retaliation. The Dan Newman company will have its own computer design a fabric featuring your name in 1/4-inch letters on 60-inch polyester fabric in your choice of seven colors. Fouryard minimum ($8.95 per yard with a $1.95 shipping charge for each four-yard order). Write: Dan Newman Company, 57 Lakeview Avenue, Clifton, N.J. 07011 CAPTION: Illustration, Krizia's gray striped coat and pants, sketched by Mariuccia Mandelli for the Washington Post; Picture 1, Basile's 9/10 coat with a shorter skirt, below; Pictures 2 and 3, then and now at the Corcoran; 1979 photo by Earl Goldstein