Atlantis completed a short expedition to the International Space Station in 2008. Upon its return to earth, the space shuttle landed at the Kennedy Space Center. Six of the shuttle’s crew members were able to exit the spacecraft without aid. The astronauts then continued standing, walking, and posing for the press. But a seventh astronaut had landed with Atlantis. NASA engineer Daniel Tani was absent from most of the press videos.
Here's a guess why: Daniel Tani had spent a full 120 days in space, while his six crew members had only been on a 12 day mission. They had picked Tani up at the space station and brought him home. Living in zero gravity affects the human body in a lot of ways, and Tani had lived like that for four months.
Astronauts are usually carried out of the space craft after long space expeditions. They are rarely able to walk around like the crew of Atlantis. Instead, they are taken to a place where they can sit and rest. This is because of a condition called Spaceflight Osteopenia, or bone loss. For every month an astronaut spends in zero gravity, they will lose more than 1% of their bone mass.
Presumably, this is why Tani was absent from the press photos. He was likely unable to walk or stand with the ease of his crew members.