Estimated read time: 3–4 minutes The Truth About Tendon Pain If you’ve ever been told to “just stretch it out” when your Achilles, knee, or elbow started to ache — you’re not alone.For years, that advice was the norm. But modern research is clear: tendons don’t respond to stretching the same way muscles do. When you feel that stiff, achy, or burning sensation in a tendon, whether it’s your Achilles after a long run or your elbow after lifting — it’s rarely because it’s too tight. It’s because the tendon’s load capacity has been exceeded.