The Belgian world number two handled the jitters better on a sunny Melbourne Park centre court, while Myskina admitted she had lost the match before it had even started.
Clijsters said she will wait until she is given the "all clear" on her ankle before taking the court for her semi-final against Patty Schnyder. Switzerland's Schnyder earlier ended Lisa Raymond's giant-killing run with a 7-6 6-3 win.
Men's third seed Juan Carlos Ferrero showed no sign of the elbow, shoulder or hamstring injuries which had threatened to scupper his hopes earlier in the tournament, fighting off stylish Hicham Arazi 6-1 7-6 7-6 to reach the last four.
He will face either Wimbledon champion Roger Federer or Argentine David Nalbandian in the last four. They play later on Wednesday.
Clijsters beat Myskina in an edgy affair and, whilst saying she would test her ankle before playing Thursday's semi-final, she added that it would take a lot to sideline her now that she is only two matches away from her maiden grand slam crown.
"I'm going to have a week off anyway after this. I might as well go for it and give myself a shot," she said.
"But on the other hand, if I can't walk tomorrow then it's stupid to go out there. But it's something that I'll have to see tomorrow," she said.
NUMBER TWO
The 20-year-old swept through the first set in 26 minutes and looked to be well in control before quickly falling behind in the second.
Myskina jumped to a 4-0 lead before the second seed could register another game. Clijsters called the trainer at 4-1 down after her ankle injury began troubling her and then got back on track.
Sixth seed Myskina missed three set points while leading 5-3 and then seemed to self-destruct, allowing Clijsters back into the match.
Clijsters netted on two match points while leading 6-5 and the set went to a tiebreak. She needed four more match points in the tiebreak before clinching the win 11-9.
Myskina said nerves had got the better of her.
"I was nervous, I think I lost this match before I even played it," the Russian said.
"I was just trying to keep the ball in but Clijsters was winning those rallies."
Schnyder, the 22nd seed, had not made it past the quarter-finals of a major tournament in nine years and was thrilled by her victory.
"It's great, overwhelming," Schnyder said. "I'm just happy to be here, to come out again and play semis and give it the best I can," she said.
"Yeah, it's enormous... it's hard to describe."
GUTSY VICTORY
Raymond, the 25th seed, had caused the biggest upset of the tournament when she ousted third seed Venus Williams in the third round with a dazzling and dominant performance.
But the American doubles specialist was defensive and erratic against Schnyder.
"To be honest, you know, I didn't really feel comfortable the whole match really," she said.
Ferrero battled into the semis here for the first time with a gutsy victory.
The wiry Spaniard, French Open champion and runner-up at the U.S. Open last year, underlined his title credentials with another hard-nosed performance in an absorbing baseline struggle.
"I knew Arazi plays good rallies and I'm just glad to win such a tough match," said Ferrero.
"My chances? I'm in the semi-finals and playing really well. (Top seed Andy) Roddick is out but I will have two great players in front of me, so it will be very difficult."
