A sprain is an injury to a ligament or joint, caused by twisting it too far, as when someone sprains an ankle stepping off a curb. A strain is an injury to a muscle or tendon, caused by overstretching or overusing it, as when someone strains their back lifting something heavy. The quickest way to remember it: sprain goes with joint, strain goes with muscle.
The core difference
A sprain hurts a ligament by twisting; a strain hurts a muscle or tendon by overstretching.
- sprain — to injure a joint or ligament by twisting it too far: She sprained her ankle stepping off the curb.
- strain — to injure a muscle or tendon by overstretching or overusing it: He strained his back lifting the sofa.
How to tell them apart
The simplest test is the type of tissue involved. Ankles, wrists and knees get sprained, because those are joints held together by ligaments that can be twisted. Backs, necks and eyes get strained, because muscles and tendons are what stretch too far when you lift something heavy or squint in dim light.
Strain has extra everyday senses that sprain does not share. It can mean a great effort, as in straining to hear a whispered conversation, or the pressure and tension something puts on you, as in the strain of long hours at work. Strain can even mean a variety of a virus or bacterium, as in a new strain of flu. Sprain, by contrast, sticks closely to its one meaning: a twisted joint or ligament.
