Even zero gravity can be bad for your joints: Scientists find cartilage breaks down in rats’ legs on the ISS as the muscular system wastes away from lack of use

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Space travel could create long-term health problems for astronauts as research finds it damages cartilage and causes arthritis.

Even short spells in space affect the body so much that it could lead to early-onset arthritis, as bones and joints interact differently in zero gravity. 

Previous analysis has shown that living and working in space leads to many changes in the human body, including the immune system, blood pressure and eye shape.

But this first-of-a-kind study from the Henry Ford Hospital, Michigan, adds to a growing body of research about the health effects of spaceflight on the skeleton.

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Risk: Even short spells in space affect the body so much that it could lead to early-onset arthritis, as bones and joints interact differently in zero gravity than they were intended

Scientists put mice on a Russian rocket for 30 days and found early signs of cartilage breakdown when they returned.

This is because of the zero gravity conditions in space that means less weight is pulling down on the musculoskeletal system.

Funded by a $100,000 (£78,921) NASA grant, the new study analysed molecular changes in the cartilage of mice that spent a month in animal research enclosures aboard an unmanned Russian Bion-M1 spacecraft in 2013.

The results were compared to mice observed on Earth during the same period.

Video footage taken of the mice showed them floating around in their enclosure during the day and struggling to climb over each at night. 

They also found it difficult to hang onto a grate inside the enclosure.

In comparison, the mice on Earth showed 'no discernible cartilage degradation', according to the team.

The study found that cartilage changes in the space mice were similar to humans who suffer from osteoarthritis.

Osteoarthritis is the most common form of arthritis, that causes joints to become painful and stiff, and while it cannot be cured, symptoms can be alleviated by specialised creams and ointments.

Investigation: Scientists from the Henry Ford Hospital in Michigan put mice on a Russian spaceflight for 30 days and looked at their musculoskeletal system upon their return

Fact: The International Space Station (ISS) is a $100 billion (£80 billion) science and engineering laboratory that orbits 250 miles (400 km) above Earth

Published online in journal Microgravity, the study says more research is needed before humans make a trip to Mars in the future.

Lead author Dr Jamie Fitzgerald, head of musculoskeletal genetics at Henry Ford's Department of Orthopedic Surgery, said: 'Overall, we can say that after 30 days of microgravity, the process of cartilage degrading began.

'We saw changes in the gene expressions that were consistent with cartilage breakdown. When there's no gravity pulling down on the cartilage, it's not able to maintain its structure, its integrity.

'The most dramatic example is the atrophy of muscle and de-mineralisation of bones that occurs during spaceflight. On Earth, every time you take a step to walk, you're loading that cartilage. In space, there's very little of that.

'When that loading is removed due to weightlessness and near zero gravity in space, these tissues begin to degrade.

'If this were to happen to humans, given enough time, it would lead to major joint problems.'

Dr Fitzgerald added that although muscle and bone loss is reversed when astronauts return to Earth, cartilage is a tissue that 'repairs very poorly'.

He said: 'Because cartilage in humans doesn't readily repair, the return to Earth could potentially bring long-term health problems.'

EXPLAINED: THE $100 BILLION INTERNATIONAL SPACE STATION SITS 250 MILES ABOVE THE EARTH

The International Space Station (ISS) is a $100 billion (£80 billion) science and engineering laboratory that orbits 250 miles (400 km) above Earth.

It has been permanently staffed by rotating crews of astronauts and cosmonauts since November 2000. 

Crews have come mainly from the US and Russia, but the Japanese space agency JAXA and European space agency ESA have also sent astronauts. 

The International Space Station has been continuously occupied for more than 20 years and has been expended with multiple new modules added and upgrades to systems 

Research conducted aboard the ISS often requires one or more of the unusual conditions present in low Earth orbit, such as low-gravity or oxygen.

ISS studies have investigated human research, space medicine, life sciences, physical sciences, astronomy and meteorology.

The US space agency, NASA, spends about $3 billion (£2.4 billion) a year on the space station program, with the remaining funding coming from international partners, including Europe, Russia and Japan.

So far 244 individuals from 19 countries have visited the station, and among them eight private citizens who spent up to $50 million for their visit.

There is an ongoing debate about the future of the station beyond 2025, when it is thought some of the original structure will reach 'end of life'.

Russia, a major partner in the station, plans to launch its own orbital platform around then, with Axiom Space, a private firm, planning to send its own modules for purely commercial use to the station at the same time. 

NASA, ESA, JAXA and the Canadian Space Agency (CSA) are working together to build a space station in orbit around the moon, and Russia and China are working on a similar project, that would also include a base on the surface. 

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