Scientists Find Hidden Cause Behind Tennis Elbow Pain

Scientists just found the molecular switch that makes tennis elbow, jumper's knee, and Achilles tendon pain so stubborn to treat.

Researchers at ETH Zurich and Balgrist University Hospital identified a protein called HIF1 as the hidden culprit behind painful tendon injuries that plague millions of athletes and older adults. Until now, doctors knew these injuries happened from overuse but couldn't pinpoint why some people's tendons broke down while others stayed strong.

The breakthrough came when the team tested HIF1 in mice and human tendon tissue collected during surgeries. Mice with HIF1 constantly switched on developed tendon disease even without overuse. Mice with HIF1 turned off stayed healthy even when their tendons were overloaded.

"Tendons must withstand powerful loads, with all the forces of our muscles being concentrated to the relatively thin tendons," explains Professor Jess Snedeker, who led the research. The protein causes harmful changes that make tendons brittle and triggers blood vessel and nerve growth into the tissue, which likely explains the persistent pain.

Lead researcher Greta Moschini discovered that higher HIF1 levels create extra crosslinks in collagen fibers, the building blocks that give tendons their strength. These crosslinks impair the tendon's mechanical function and make the tissue more prone to injury.

The finding matters most for young athletes whose tendon problems are still treatable. Over time, HIF1-related damage can become permanent, leaving surgery as the only option to remove diseased tissue.

The Bright Side

This discovery transforms tendinopathy from a mysterious condition into one with a clear biological target. Physical therapy currently offers only modest improvement for severe cases, leaving patients frustrated and in pain.

Now researchers are hunting for ways to block HIF1 specifically in tendons without affecting the rest of the body, where the protein plays important roles. Professor Katrien De Bock's team is studying molecules influenced by HIF1 to find safer, more precise treatment targets.

The research opens a path toward preventing these injuries before they become permanent. Early treatment could stop HIF1 damage from accumulating, keeping active people moving pain-free for decades longer.

Understanding the root cause means future treatments could actually reverse tendon disease instead of just managing symptoms.