Eighteen days in orbit did not appear to leave a measurable mark on the hips, knees, or ankles of three astronauts from Axiom Mission 4, according to new research from National Jewish Health. The result is reassuring on its own. Just as important, the work points to a portable imaging tool. This could help doctors keep closer watch on joint health during future missions. This is especially relevant as space agencies look toward longer stays in orbit and eventual trips to the Moon and Mars. That tool is musculoskeletal ultrasound, a noninvasive scan more often associated with clinics on Earth than with astronaut medicine. In this pilot study, rheumatologists used it to examine cartilage, synovial fluid, tendons, and ligaments before launch. They also examined the astronauts again within four hours after splashdown. They found no statistically significant changes in the astronauts’ lower-extremity joint structures after the short mission aboard the International Space Station. For a field concerned about what microgravity does to the human body, that matters. Scientists have long known that reduced loading in …