: A fluid-filled sac that forms behind the knee, often causing a bulge and a feeling of tightness.
: Inflammation of the small, deep muscle that helps "unlock" your knee when you start to bend it. Pain in the back of my knee – Mr Validity
Pain in the back of the knee, often called , can stem from several common issues. If you are specifically looking for Mr Validity (likely referring to the sports injury and wellness brand Validity), they focus on recovery tools and education for athletes. Common Causes of Posterior Knee Pain : A fluid-filled sac that forms behind the