Editing Sprain (section)

== Causes ==
Acute sprains typically occur when the joint is abruptly forced beyond its functional range of motion, often in the setting of trauma or sports injuries. The most common cause of sprains in general is repetitive movements (overuse).<ref>{{cite web |title=Sprains and Strains: Differences, Treatment, Symptoms, 3 Grades & Causes |url=https://www.medicinenet.com/sprained_ankle/article.htm |website=MedicineNet |language=en}}</ref>

=== Mechanism ===
[[Ligament]]s are [[collagen]] fibers that connect [[bone]]s together, providing passive stabilization to a joint. These fibers can be found in various organizational patterns (parallel, oblique, spiral, etc.) depending on the function of the joint involved. Ligaments can be extra-capsular (located outside the joint capsule), capsular (continuation of the joint capsule), or intra-articular (located within a joint capsule).<ref name=":3" /> The location has important implications for healing as blood flow to intra-articular ligaments is diminished compared to extra-capsular or capsular ligaments.<ref>{{Cite journal|last=Frank|first=C. B.|date=June 2004|title=Ligament structure, physiology and function|journal=Journal of Musculoskeletal & Neuronal Interactions|volume=4|issue=2|pages=199–201|issn=1108-7161|pmid=15615126}}</ref>

Collagen fibers have about a 4% elastic zone where fibers stretch out with increased load on the joint. However, exceeding this elastic limit causes a rupture of fibers, leading to a sprain. It is important to recognize that ligaments adapt to training by increasing the cross-sectional area of fibers.<ref>{{Cite journal|last1=Doschak|first1=M. R.|last2=Zernicke|first2=R. F.|date=March 2005|title=Structure, function and adaptation of bone-tendon and bone-ligament complexes|journal=Journal of Musculoskeletal & Neuronal Interactions|volume=5|issue=1|pages=35–40|issn=1108-7161|pmid=15788869}}</ref> When a ligament is immobilized, the ligament has been shown to rapidly weaken. Normal daily activity is important for maintaining about 80–90% of the mechanical properties of a ligament.<ref name=":3" />

=== Risk factors ===

* [[Fatigue (medical)|Fatigue]] and overuse<ref name=":3" />
* High-intensity [[contact sport]]s
* Environmental factors
* Poor [[Exercise|conditioning]] or equipment<ref name=":4" />
*Age and [[genetic predisposition]] to ligament injuries<ref>{{Cite journal|url=http://www.eurekaselect.com/123267/article|title=Unravelling the Genetic Susceptibility to Develop Ligament and Tendon Injuries|last1=Longo|first1=Umile Giuseppe|last2=Loppini|first2=Mattia|date=2014-12-31|journal=Current Stem Cell Research & Therapy|language=en|doi=10.2174/1574888x09666140710112535|access-date=2020-04-20|last3=Margiotti|first3=Katia|last4=Salvatore|first4=Giuseppe|last5=Berton|first5=Alessandra|last6=Khan|first6=Wasim S.|last7=Denaro|first7=Nicola Maffulli and Vincenzo|volume=10|issue=1|pages=56–63|pmid=25012736|url-access=subscription}}</ref>
* Lack of stretching or "[[warming up]]", which when performed properly increases [[Hemodynamics|blood flow]] and joint flexibility<ref>{{Cite journal|last1=Woods|first1=Krista|last2=Bishop|first2=Phillip|last3=Jones|first3=Eric|date=2007-12-01|title=Warm-Up and Stretching in the Prevention of Muscular Injury|journal=Sports Medicine|language=en|volume=37|issue=12|pages=1089–1099|doi=10.2165/00007256-200737120-00006|pmid=18027995|s2cid=27159577|issn=1179-2035}}</ref>