Knee dislocations are rare, but a significant number have serious associated neurovascular injury. This article discusses tibiofemoral joint dislocation.
Please see separate articles for discussion of medial and lateral patellar dislocations.
They account for <0.5% of all joint dislocations. Knee dislocations are bilateral in 5% of cases 1,4.
Dislocation of the knee is usually obvious clinically with a marked deformity. It is seen in the context of both high and low energy trauma. There is a high risk of neurovascular sequelae and therefore rapid assessment and definitive treatment is essential.
- damage to the popliteal artery occurs in ~30% (range 20-30%) 1,3,4
- nerve damage is reported in ~30% (range 16-40%) with the common peroneal nerve more commonly injured than the tibial nerve 1,3,4
Five types of knee dislocation have been described, with respect to tibial displacement compared to the femur 1,2,4:
- anterior (40%)
- posterior (~33%)
- lateral (~20%)
- rotatory (~5%)
- medial (~5%)
Knee dislocations are invariably associated with ligamentous injuries. The most common pattern is bicruciate (i.e. both anterior and posterior) cruciate ligament tears with either medial collateral ligament tear or posterolateral corner injury 4. Fractures of the distal femur or proximal tibia are also common (~15%) 2,4.
Forced hyperextension is the most common mechanism of injury, and can occur in both high-velocity (e.g. motor vehicle collisions) and low-velocity (e.g. sports injuries) trauma.
The Schenck classification categorizes knee dislocation based on the pattern of multiligamentous injury and is the usual system used by sports medicine physicians; it has superseded the older position classification system . Trauma surgeons tend to use a different classification based on the energy and velocity of the trauma 5.
Treatment and prognosis
The management of dislocations in the emergency department firstly requires immediate reduction of the knee joint, ideally as a closed procedure. A rapid neurovascular assessment is then performed. In posterolateral dislocation a closed reduction may be impossible, in which case an open reduction is necessary 2.
Once the knee joint has been relocated, further management depends on the age and activity of the patient. Generally a non-interventionist rehabilitation is advocated in those who are more sedentary, or of advancing age. The mainstay of this approach is immobilization. Although this may lead to a stable joint, mild dysfunction is often a problem. Thus a conservative approach is generally not felt to be appropriate in younger, more active individuals.
Therefore surgical intervention is now advocated for this latter cohort, with usually better functional outcomes. The main criterion for surgical repair rests on the severity of ligamentous injury 2.
- 1. Walker RE, McDougall D, Patel S et-al. Radiologic review of knee dislocation: from diagnosis to repair. AJR Am J Roentgenol. 2013;201 (3): 483-95. doi:10.2214/AJR.12.10221 - Pubmed citation
- 2. Henrichs A. A review of knee dislocations. (2004) Journal of athletic training. 39 (4): 365-9. Pubmed
- 3. ACSM's primary care sports medicine. LWW. ISBN:0781770289. Read it at Google Books - Find it at Amazon
- 4. Robertson A, Nutton RW, Keating JF. Dislocation of the knee. J Bone Joint Surg Br. 2006;88 (6): 706-11. doi:10.1302/0301-620X.88B6.17448 - Pubmed citation
- 5. Schenck RC, Richter DL, Wascher DC. Knee Dislocations: Lessons Learned From 20-Year Follow-up. (2014) Orthopaedic journal of sports medicine. 2 (5): 2325967114534387. doi:10.1177/2325967114534387 - Pubmed
Related Radiopaedia articles
The knee is a complex synovial joint that can be affected by a range of pathologies:
- bone and cartilage
- distal femoral condyle fracture
- tibial plateau fracture (classification)
- patella fracture
avulsion fractures of the knee
- Segond fracture
- reverse Segond fracture
- anterior cruciate ligament avulsion fracture
- posterior cruciate ligament avulsion fracture
- arcuate complex avulsion fracture (arcuate sign)
- biceps femoris avulsion fracture
- iliotibial band avulsion fracture
- semimembranosus tendon avulsion fracture
- Stieda fracture (MCL avulsion fracture)
- patella fracture
- chronic avulsion injuries
- chondromalacia patellae
- osteoarthritis of the knee
- osteochondral defects
- osteochondritis dissecans of the knee
- pattern of bone contusion in knee injuries
- knee fractures
- anterior cruciate ligament tear
- anterior cruciate ligament ganglion cyst
- anterior cruciate ligament mucoid degeneration
- posterior cruciate ligament tear
- medial collateral ligament tear
- lateral collateral ligament tear
- medial patellofemoral ligament tear
- posterolateral corner injury
- posteromedial corner injury
- meniscal lesions
- meniscal tear
- meniscal/parameniscal cyst
- meniscal flounce
- meniscal fraying
- meniscocapsular separation
- floating meniscus
- bursosynovial lesions
- fat pad
- popliteal fossa