Ariza, who had been UCLA's leadng scorer in its two exhibition games this season, was discovered to have the condition the day before the first non-conference game against Vermont.
Spontaneous pneumothorax is where a portion of the lung collapses.
Ariza has undergone tests since it was discovered, which have all showed no signs of any abnormality. He hasn't practice until just recently, waiting for his lungs to fully inflate after the collapse.
Ariza was cleared earlier this week to practice lightly, but then participated full-speed in a good portion of practice Friday. He's still scheduled to have x-rays next week for precautionary reasons.
"His minutes will be very limited against Loyola Marymount," head coach Ben Howland said. "I'm very happy for Trevor and I'm excited for our team to have him back in the lineup."