Unhappy Triad
Introduction
The unhappy triad classically refers to three injuries occurring together from acute trauma: the ACL, the medial meniscus. and the MCL.
It was first described by O'Donoghue in 1950 as a constellation of injuries that commonly occurred together in the acute sporting context - the ACL, the medial meniscus, and the medial collateral ligament.[1] O'Donoghue estimated the condition had a 25% prevalence rate in acute athletic injuries.[1] Various authors would later go on to describe their own findings, that it was more common for the lateral meniscus to be injured alongside the ACL and MCL, instead of the medial meniscus.[2][3][4][5][6] It has thus been suggested that the unhappy triad should instead describe the combination of injuries to the ACL, the lateral meniscus, and the MCL.[2]
Anatomy
The Unhappy Triad is modernly understood to refer to a combination of injuries to the ACL, the lateral meniscus, and the MCL. The classical version uses the medial meniscus instead of the lateral meniscus.
Mechanism of Injury
The mechanism of injury for the unhappy triad is sudden valgus impact i.e. a lateral force with external or internal rotation is applied to the knee.[7] The triad often occurs in both contact and non-contact sports such as soccer, netball, basketball, rugby, and skiing.[4][8]
Clinical Presentation
Swelling and hemorrhage form after hours, from the meniscal and ligament injuries. Pain and impaired muscle control may present acutely. The unhappy triad can cause osteoarthritis in 50% of patients after 10-20 years due to intra-articular processes initiated due to the injury.[9]
Physical Examination
As 25% of acute knee injuries are due to the unhappy triad, clinicians should be ready to examine their components during the physical examination.
Unhappy Triad (Modern version):[7][10]
MCL
The MCL can be examined through the
- palpation
ACL
The ACL can be examined by:
Lateral meniscus
Lateral meniscus is examined by:
- McMurray's test
- Apley's test
- Thessaly test
- Lateral tibiofemoral joint line palpation
Unhappy Tetrad
Recent research has suggested another associated injury with the unhappy triad - expanding the term to the 'unhappy tetrad' and including one more injury: damage/ a tear to the anterolateral ligament.[11] [12][13]Pivot-shift tests, such as the jerk test, can be used to assess anterolateral rotatory instability after a tear to the anterolateral ligament.[14]
Management
Most cases require surgery and a recovery period of 6 to 9 months.[9] Patients with the unhappy knee triad (tetrad) injury with MCL injuries of grade I or II can opt for initial conservative treatment via injections and physiotherapy, with a delay in ACL reconstruction, to first allow the MCL to heal by itself.[13]Read more on MCL conservative treatment here.
Grade III injuries or competitive athletes are better treated surgically because of the risk of future knee osteoarthritis and valgus knee instability.[15]
References
- ↑ 1.0 1.1 O'donoghue D (1964) The unhappy triad: etiology, diagnosis and treatment. Am J Orthop 6:242–247
- ↑ 2.0 2.1 Shelbourne KD, Nitz PA (1991) The O’Donoghue triad revisited. Combined knee injuries involving anterior cruciate and medial collateral ligament tears. Am J Sports Med 19(5):474–477. https://doi. org/10.1177/036354659101900509
- ↑ Barber FA (1992) What is the terrible triad? Arthroscopy 8(1):19– 22. https://doi.org/10.1016/0749-8063(92)90130-4
- ↑ 4.0 4.1 Dacombe PJ (2013) Shelbourne’s update of the O'Donoghue knee triad in a 17-year-old male Rugby player. BMJ Case Rep 23:2013. https://doi.org/10.1136/bcr.01.2012.5593
- ↑ Mansori AE, Lording T, Schneider A, Dumas R, Servien E, Lustig S (2018) Incidence and patterns of meniscal tears accompanying the anterior cruciate ligament injury: possible local and generalized risk factors. Int Orthop 42(9):2113–2121. https://doi.org/10.1007/ s00264-018-3992-x
- ↑ Vielgut I, Dauwe J, Leithner A, Holzer LA (2017) The fifty highest cited papers in anterior cruciate ligament injury. Int Orthop 41(7): 1405–1412. https://doi.org/10.1007/s00264-017-3513-3
- ↑ 7.0 7.1 Ferretti A, Monaco E, Fabbri M, Maestri B, De Carli A. Prevalence and classification of injuries of anterolateral complex in acute anterior cruciate ligament tears. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2017 Jan 1;33(1):147-54.
- ↑ Bollier M, Smith PA. Anterior cruciate ligament and medial collateral ligament injuries. The journal of knee surgery. 2014 Oct;27(05):359-68.
- ↑ 9.0 9.1 Hoveidaei AH, Sattarpour R, Dadgostar H, Razi S, Razi M. Unhappy triad of the knee: What are the current concepts and opinions? World J Orthop. 2023 May 18;14(5):268-274. doi: 10.5312/wjo.v14.i5.268. PMID: 37304199; PMCID: PMC10251265.
- ↑ Hughston JC, Andrews JR, Cross MJ, MoscHI AR. Classification of knee ligament instabilities. Part I. The medial compartment and cruciate ligaments. JBJS. 1976 Mar 1;58(2):159-72.
- ↑ Schmitt O, Mittelmeier H. The biomechanical significance of the vastus medialis and lateralis muscles. Archives of orthopaedic and traumatic surgery. 1978 Dec;91:291-5.
- ↑ Müller W. The knee: form, function, and ligament reconstruction. (e-pub ahead of print 1983)
- ↑ 13.0 13.1 Ferretti A, Monaco E, Ponzo A, Dagget M, Guzzini M, Mazza D, Redler A, Conteduca F. The unhappy triad of the knee re-revisited. Int Orthop. 2019 Jan;43(1):223-228. doi: 10.1007/s00264-018-4181-7. Epub 2018 Oct 1. PMID: 30276447.
- ↑ McCluskey G, Blackburn TA. Classification of knee ligament instabilities. Physical Therapy. 1980 Dec 1;60(12):1575-7.
- ↑ Narvani A, Mahmud T, Lavelle J, Williams A. Injury to the proximal deep medial collateral ligament: a problematical subgroup of injuries. The Journal of Bone & Joint Surgery British Volume. 2010 Jul 1;92(7):949-53.