{{Infobox medical condition (new) | name = | synonyms = Broken kneecap | image = Fracpetella.PNG | caption = A fracture of the patella seen on a lateral view | pronounce = | field = Orthopedics | symptoms = Pain, swelling, bruising to front of the knee<ref name=AO2017/> | complications = Injury to the tibia, femur, or knee ligaments<ref name=Ka2016/> | onset = | duration = | types = Stable, displaced, comminuted, open<ref name=AO2017/> | causes = Trauma to the front of the knee<ref name=AO2017/> | risks = | diagnosis = Based on symptom, confirmed with X-rays.<ref name=Bul2017/> | differential = Bipartite patella<ref name=Bul2017/> | prevention = | treatment = Casting, splinting, surgery<ref name=Ka2016/> | medication = | prognosis = Generally good with treatment<ref name=Ka2016/> | frequency = ~ 1% of fractures<ref name=Bul2017/> | deaths = }} <!-- Definition and symptoms --> A '''patella fracture''' is a break of the kneecap.<ref name=AO2017>{{cite web|title=Patellar (Kneecap) Fractures|url=http://orthoinfo.aaos.org/topic.cfm?topic=a00523|website=OrthoInfo - AAOS|access-date=16 October 2017|date=January 2017|url-status=live|archive-url=https://web.archive.org/web/20171016230105/http://orthoinfo.aaos.org/topic.cfm?topic=a00523|archive-date=16 October 2017}}</ref> Symptoms include pain, swelling, and bruising to the front of the knee.<ref name=AO2017/> A person may also be unable to walk.<ref name=AO2017/> Complications may include injury to the tibia, femur, or knee ligaments.<ref name=Ka2016>{{cite journal | vauthors = Kakazu R, Archdeacon MT | title = Surgical Management of Patellar Fractures | journal = The Orthopedic Clinics of North America | volume = 47 | issue = 1 | pages = 77–83 | date = January 2016 | pmid = 26614923 | doi = 10.1016/j.ocl.2015.08.010 }}</ref>
<!-- Cause and diagnosis --> It typically results from a hard blow to the front of the knee or falling on the knee.<ref name=AO2017/>The patella can also be fractured indirectly. For example, a sudden contraction of the quadriceps muscle in the knee can pull apart the patella.<ref name=AO2017/>Diagnosis is based on symptoms and confirmed with X-rays.<ref name=Bul2017>{{cite web| vauthors = Abbasi D |title=Patella Fracture - Trauma|url=https://www.orthobullets.com/trauma/1042/patella-fracture|website=Orthobullets.com|access-date=16 October 2017|language=en|url-status=live|archive-url=https://web.archive.org/web/20171017042146/https://www.orthobullets.com/trauma/1042/patella-fracture|archive-date=17 October 2017}}</ref> In children an MRI may be required.<ref name=Bul2017/>
<!-- Treatment --> Treatment may be with or without surgery, depending on the type of fracture.<ref name=Ka2016/> Undisplaced fracture can usually be treated by casting.<ref name=Ka2016/> Even some displaced fractures can be treated with casting as long as a person can straighten their leg without help.<ref name=Ka2016/> Typically the leg is immobilized in a straight position for the first three weeks and then increasing degrees of bending are allowed.<ref name=Ka2016/> Other types of fractures generally require surgery.<ref name=Ka2016/><ref>{{cite journal | vauthors = Melvin JS, Mehta S | title = Patellar fractures in adults | journal = The Journal of the American Academy of Orthopaedic Surgeons | volume = 19 | issue = 4 | pages = 198–207 | date = April 2011 | pmid = 21464213 | doi = 10.5435/00124635-201104000-00004 | s2cid = 34028631 }}</ref>
<!-- Epidemiology --> Patella fractures make up about 1% of all broken bones.<ref name=Bul2017/> Males are affected more often than females.<ref name=Bul2017/> Those of middle age are most often affected.<ref name=Bul2017/> Outcomes with treatment are generally good.<ref name=Ka2016/>
==Signs and symptoms== Also known as a broken kneecap, a patella fracture usually follows a history of trauma and commonly presents with swelling, pain, bruising and inability to both bend and straighten the knee.<ref name=Lee2010>{{cite book| vauthors = Lee D, Li B, Grannis S |chapter= Chapter 11: Knee |title=Orthopedic Rehabilitation Clinical Advisor | chapter-url=https://books.google.com/books?id=RKxpdpuVb0wC&q=patella+fracture&pg=PA592 |publisher=Mosby Elsevier |year=2010 |isbn=978-0-323-05710-3 | veditors = Sueki D, Brechter J |location=|page=592 }}</ref> The pain is worse when trying to stand and the person may be unable to walk. The pain can also be aggravated by prolonged periods of sitting.<ref name=AO2017/><ref name=Lee2010/> A painful defect may be felt in the knee and there may be blood in the joint.<ref name=Bedi2010/>
===Complications=== Complications may include injury to the tibia, femur, or knee ligaments.<ref name=Ka2016/> In the longer term, the knee may not regain full movement, pain may persist and there is an increased likelihood of osteoarthritis of the knee.<ref name="ECI">{{cite web |title=Patella Fractures |url=https://aci.health.nsw.gov.au/networks/eci/clinical/clinical-resources/clinical-tools/orthopaedic-and-musculoskeletal/musculoskeletal-orthopaedic-guide/patella-fractures |website=Emergency Care Institute (ECI) |publisher=Emergency Care Institute new South Wales |access-date=14 February 2021 |language=en |date=1 September 2016 |archive-date=19 June 2019 |archive-url=https://web.archive.org/web/20190619063259/https://www.aci.health.nsw.gov.au/networks/eci/clinical/clinical-resources/clinical-tools/orthopaedic-and-musculoskeletal/musculoskeletal-orthopaedic-guide/patella-fractures }}</ref> If there is an associated open wound as in an open fracture, complications also include risk of infection, inability of the broken bones to reunite and osteonecrosis.<ref name="ECI"/>
==Diagnosis== thumb|upright|A vertical patella fracture with the fracture line marked by a red arrow Diagnosis is based on symptoms and confirmed with X-rays.<ref name=Bul2017/> In children an MRI may be required.<ref name=Bul2017/>
===Differential diagnosis=== thumb|Bipartite patella Some people have a normal bipartite patella or two-part patella which can appear as a fracture. The fragment is usually seen in the top outer corner of the patella and can be distinguished from a fracture by being present in both knees.<ref name="Bedi2010">{{Cite book| vauthors = Bedi A, Karunakar MA |chapter-url= https://books.google.com/books?id=OhVSFNEIanIC&pg=PA1752 |title=Rockwood and Green's Fractures in Adults |date=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-1-60547-677-3| veditors = Rockwood CA, Bucholz RW, Court-Brown CM, Heckman JD, Tornetta P |edition=7th|location=Philadelphia|pages=1752–1765|language=en|chapter=52. Patella fractures and extensor mechanism injuries}}</ref>
===Types=== The patella can break in various ways depending on the way it is injured, and into two or more pieces.<ref name=AO2017/> Types include transverse, the most common, with one fracture line;<ref name=Lee2010/> marginal; osteochondral; and the rare vertical type, or stellate, where a direct compression force gives rise to a comminuted pattern.<ref name=Lee2010/><ref name="ECI"/> Patella fractures can be further classified as displaced, where the broken ends of bone do not line up correctly and separate by more than 2mm, or undisplaced and stable where pieces of bone remain in contact with each other.<ref name=AO2017/><ref name="ECI"/> If fragments of patella bone stick out from the skin it is known as an open patella fracture, and closed if the overlying skin is intact.<ref name=AO2017/>
<gallery widths="200px" heights="200px" > File:Patellaquerfraktur seitlich.jpg|Transverse fracture of patella File:ZP+B fraktura patelly (39).jpg|Comminuted fracture of patella File:Patellafraktur laengs.jpg|Osteochondral fracture of patella File:Patella fracture.JPG|Vertical patella fracture </gallery>
==Treatment== Treatment may be with or without surgery, depending on the type of fracture and whether the overlying skin is intact or broken.<ref name=Ka2016/>
===Conservative=== Undisplaced fractures can usually be treated by casting.<ref name=Ka2016/> Even some displaced fractures can be treated with casting as long as the person can straighten their leg without help, thus confirming that the quadriceps mechanism of the leg is intact.<ref name=Ka2016/><ref name=Wilde2010/> In this case the leg is immobilized in a straight position for the first three weeks and then increasing degrees of bending are allowed as healing occurs.<ref name=Ka2016/>
===Surgery=== thumb|Tension band wiring: front and side view Most patella fractures are transverse or comminuted, hence the quadriceps mechanism is disrupted and they are treated by a combination of wires in a tension band construct. This unites the fractured bones, reconstructing the straightening mechanism of the leg.<ref name=Lee2010/><ref name="Bedi2010"/>
If the patella is broken in several places, that is comminuted, then traditionally a patellectomy (removal of the whole patella) is performed in order to reconstruct the extensor mechanism and prevent the onset of an extension lag at the knee joint, resulting in instability.<ref name=Lee2010/><ref name=Wilde2010/><ref>{{cite journal | vauthors = Günal I, Karatosun V | title = Patellectomy: an overview with reconstructive procedures | journal = Clinical Orthopaedics and Related Research | volume = 389 | issue = 389 | pages = 74–78 | date = August 2001 | pmid = 11501826 | doi = 10.1097/00003086-200108000-00012 }}</ref> Some surgeons however would rather opt for internal fixation.<ref name=Wilde2010/> A partial patellectomy is removal of only a portion of the patella, and may be carried out if at least 60% of the patella can be maintained.<ref name=Bedi2010/><ref name=Wilde2010>{{cite book| vauthors = Wilde PG |url=https://books.google.com/books?id=_ajRAQAAQBAJ|title=Medicolegal Reporting in Orthopaedic Trauma E-Book|publisher=Churchill Livingstone Elsevier|year=2010|isbn=978-0-443-06833-1| veditors = Foy MA, Fagg PS |edition=4th |location= |pages=279–281 |language=English |chapter= Chapter 12: The Knee}}</ref>
Open fractures of the patella require emergency treatment with irrigation, debridement and fixation.<ref name=Bedi2010/>
===Rehabilitation=== Irrespective of surgical or non-surgical resolution to the fracture, a physical therapist can advise on progressive weight-bearing exercises and help with strengthening muscles of the leg, improving range of motion of the knee and in reducing stiffness.<ref name=AO2017/><ref name=Lee2010/>
==Prognosis== Outcomes with treatment are generally good,<ref name=Ka2016/> unless there is involvement of the articular surface or the quadriceps mechanism. There is an increased risk of developing osteoarthritis in people who have broken their patella.<ref name=Wilde2010/>
There is limited evidence supporting the different surgical interventions for treating fractures of the patella in adults.<ref name=":0">{{cite journal | vauthors = Sayum Filho J, Lenza M, Tamaoki MJ, Matsunaga FT, Belloti JC | title = Interventions for treating fractures of the patella in adults | journal = The Cochrane Database of Systematic Reviews | volume = 2021 | issue = 2 | article-number = CD009651 | date = February 2021 | pmid = 33625743 | pmc = 8095054 | doi = 10.1002/14651858.cd009651.pub3 }}</ref> There is also no evidence of trials that could evaluate the effects of surgical treatment compared with the conservative treatment or other different types of conservative interventions.<ref name=":0" />
==Epidemiology== Patella fractures make up about 1% of all broken bones.<ref name="Bedi2010"/> Males are affected more often than females.<ref name=Bul2017/> Those of middle age are most often affected.<ref name=Bul2017/> 6% to 9% of patellar fractures are of the open type.<ref name="Luo2020">{{cite book | vauthors = Luo TD, Marino DV, Pilson H | chapter = Patella Fractures | title = StatPearls |date=2020 | chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK513330/ |access-date=14 February 2021 | location = Treasure Island (FL) |publisher=StatPearls Publishing| pmid = 30020702 }}</ref> An ageing population and global increase in the number of TKAs (total knee arthroplasty) has led to an increasing number of periprosthetic fractures of which a patella fracture is one type.<ref name="Luo2020"/>
==History== Prior to the 19th century most patella fractures were treated non-surgically with extension splinting, frequently resulting in poorly joined fragments of bone and long-term pain and disability.<ref name="Bedi2010"/> Incomplete understanding of the importance of the patella led to the trend of removing the whole patella, also resulting in pain, disability and dissatisfaction.<ref name=Bedi2010/> The first open reduction and internal fixation for a patella fracture was performed in 1877 by Scottish surgeon Sir Hector Cameron.<ref name=Bedi2010/> Several techniques followed and materials used included metal loops, pins, kangaroo tendons and screws. Significant advances in surgery occurred in the 1950s with the development of banding after Herbert A. Haxton and others demonstrated that the patella was not just to protect the knee but important for straightening the leg.<ref name=Bedi2010/> Subsequently, the three surgical treatments for displaced patella fractures became tension banding, partial patellectomy and total patellectomy, the decision of which to use tailored to the individual.<ref name=Bedi2010/>
== See also == * Knee replacement (total knee arthroplasty, TKA)
== References == {{reflist}}
== External links == {{Medical resources | ICD10 = {{ICD10|S|82|0|s|80}} | AO = 34-A1 - 34-C3 | eMedicine1 = 825572 | OrthoInfo = a00523 }} {{Fractures}}
Category:Bone fractures Category:Knee injuries Category:Patella Category:Wikipedia medicine articles ready to translate