strain
Meaning of strain: The muscle counterpart of a sprain, and a word carrying a completely unrelated second meaning in microbiology.
Definition of strain
A strain is an injury to a muscle or to the tendon anchoring it to bone, caused by stretching or loading the fibers beyond what they can take. Fibers tear on a scale running from a few of them to the whole muscle belly, producing sudden pain, weakness, and later stiffness and bruising. The hamstring, calf, groin and lower back are the usual sites.
How is a strain different from a sprain?
The two words are separated only by the tissue involved, and they are swapped constantly. A strain damages muscle fibers or the tendon anchoring them, while a sprain damages a ligament running between two bones. A useful anchor is that a tendon attaches muscle to bone whereas a ligament attaches bone to bone, so a strain sits along a moving unit and a sprain sits across a joint.
| Feature | Sprain | Strain |
|---|---|---|
| Tissue injured | Ligament, bone to bone | Muscle or tendon, muscle to bone |
| Usual mechanism | Joint twisted past its range | Muscle stretched while contracting |
| Where it hurts | Over the joint line | Within the muscle belly or its tendon |
| Common sites | Ankle, knee, wrist, thumb | Hamstring, calf, groin, lower back |
| What is reported | The joint feels loose | The muscle feels weak and tight |
What else does the word strain mean?
A strain of bacteria or of a virus is a line descended from a single isolated sample, differing genetically from other lines of the same species. That sense has no connection with the injury: it descends from an old English word for offspring, while the injury sense arrives through French from Latin. A probiotic product names its specific strains for exactly that reason. Strain also describes stretching in engineering, and eye strain names tired eye muscles rather than any tearing at all.
What gets mistaken for a muscle strain?
Several things, because muscle pain is unspecific. Aching across the thighs and shoulders that builds over weeks may reflect an inflammatory muscle condition or a reaction to a medicine, since a statin such as atorvastatin can produce muscle pain and weakness with no injury behind it. Calf pain with swelling raises the question of a clot in a deep vein, which is why a calf described as a pulled muscle is examined rather than assumed. Shin pain worsening with running can be a stress fracture in the bone beneath. Pain traveling down the back of the leg may arise from a nerve root at the spine rather than from the hamstring.
Also known as
Used in a sentence
A hamstring strain was recorded after the injury occurred during sprinting.
Good to know
Strain names an injury to muscle or tendon and, in an entirely unrelated sense, a genetic line of a microorganism, so the surrounding words decide which meaning applies.
Word origin
Where “strain” comes from
The injury sense reaches English through Old French from the Latin stringere, to draw tight. The microbiology sense is a separate word, from an Old English term for offspring or lineage.