The term double-jointed describes individuals who have an abnormally large range of motion in a given joint. this excess range of motion is not because of the presence of a second joint
Hypermobility: Causes, Treatments and Exercises
3 Ways to Know if You're Double Jointed - wikiHow
Hypermobility Syndrome - Therapies For Kids
So you've noticed you're bendy? | Central Health Physiotherapy
Lower extremity energy absorption strategies at different phases during single and double-leg landings with knee valgus in pubertal female athletes | Scientific Reports