Mechanism and features of injury
The injury occurs as a result of a severe direct or indirect impact to the knee joint area.
Normal knee stability is maintained by the collateral and cruciate ligaments, menisci, and muscles (specifically the extensor mechanism). In a complete dislocation, catastrophic destruction occurs: the joint capsule and ligaments (the cruciate ligaments are invariably torn) are ruptured, and the menisci are often damaged. The anatomical proximity of the popliteal neurovascular bundle makes it extremely vulnerable to compression or overstretching at the moment of bone displacement.
Classification of knee dislocations
Depending on the direction in which the tibia is displaced relative to the femur, the following types of dislocations are distinguished:
- Anterior;
- Posterior;
- Side (medial and lateral);
- Rotational (a combination of lateral and anteroposterior displacement).
In clinical practice, the anterolateral displacement variant is the most common.
Clinical presentation and diagnostics
Immediately after the injury, the patient experiences acute pain, the limb loses its weight-bearing capacity, and active movements become impossible.
In a complete dislocation, the leg is usually straightened and visually shortened, with a pronounced bayonet-like deformity observed in the joint area. In subluxations, the joint is also deformed, but the leg may be in a slightly flexed position.
Crucial rule: if a knee dislocation is suspected, checking the range of passive motion is strictly prohibited! This can lead to irreparable damage to the popliteal artery and vein.
Approaches to ligamentous repair
A knee dislocation always entails ligament ruptures that require complex treatment to restore stability. The main goal is the formation of compensated joint instability.
Conservative treatment (a plaster cast for 6 weeks following arthrocentesis) is permissible only in cases of partial ruptures. In complete ruptures of the collateral ligaments, a conservative approach leads to chronic instability (especially for the fibular collateral ligament, which is incapable of scarring).
Surgical treatment:
- Optimal within the first 7 days (percutaneous repair of the tibial collateral ligament is possible).
- In late stages or in case of a fibular ligament rupture, only open techniques are used (plastic reconstruction, autograft reinforcement).
For cruciate ligaments in highly active patients, arthroscopic reconstruction (without arthrotomy) is the modern standard. A mandatory condition for the success of any treatment is competent rehabilitation with exercise therapy to strengthen stabilizing muscles, in order to avoid atrophy due to prolonged bracing.
Briefly: answers to topical questions
What are the absolute indications for emergency surgical intervention in a knee dislocation?
An absolute indication for emergency surgery in a knee dislocation is vascular injury with the development of acute limb ischemia. Surgery is required if ischemia persists and pulses are absent in the distal arteries after reduction of the tibia. In such cases, emergency exploration of the vascular bundle in the popliteal region and vascular repair are indicated to eliminate ischemia and prevent complications.
What does prehospital first aid involve when a knee dislocation is suspected?
Prehospital first aid consists of anti-shock measures and mandatory hospitalization of the patient.
The set of measures includes:
- Pain management — adequate analgesia to relieve pain.
- Transportation immobilization — splinting the limb from the gluteal fold to the toes.
- Infusion therapy — for the prevention and treatment of shock.
It is strictly forbidden to attempt to correct the deformity independently at the prehospital stage, as this carries a high risk of additional damage to the popliteal artery and nerves.
What instrumental diagnostic methods are mandatory when a knee dislocation is suspected?
When a knee dislocation is suspected, radiography in two standard projections is a mandatory instrumental diagnostic method. This study helps clarify the nature of the dislocation and identify possible concomitant bone injuries. Details of capsuloligamentous capsule damage are not assessed prior to reduction of the dislocation. Subsequently, before performing reconstructive surgery on the stabilizing structures of the knee joint, the diagnostic workup is supplemented by ultrasound, MRI, and arthroscopy.
Which nerves are part of the popliteal neurovascular bundle, which is vulnerable during a knee dislocation?
The neurovascular bundle of the popliteal fossa, the elements of which are vulnerable during a knee dislocation, includes the tibial nerve. The common fibular nerve also runs in this area and is frequently injured in this trauma.
- Tibial nerve (n. tibialis) — located more superficially and laterally to the popliteal vein in the popliteal fossa.
- Common fibular nerve (n. fibularis [peroneus] communis) — runs from the upper angle of the popliteal fossa to the neck of the fibula.
Class and exam questions
Why is checking passive movements contraindicated in knee dislocations?
Due to the high risk of additional compression or rupture of the popliteal vessels, which are anatomically closely adjacent to the posterior surface of the joint capsule.
Is it possible to sustain a knee dislocation without rupturing the cruciate ligaments?
No, a true knee dislocation cannot occur without the rupture of both cruciate ligaments, as it is they that restrict the anteroposterior displacement of the articular surfaces.
What are the risks of prolonged conservative immobilization in complete tears of the knee ligaments?
It is guaranteed to lead to the development of chronic joint instability, as well as cause pronounced hypotrophy of the thigh and calf muscles.
What else to study on this topic
- Methods for reducing hip dislocations (Janelidze, Kocher techniques)
- Meniscal injuries and indications for arthroscopic revision
- Classification of distal femoral and tibial plateau fractures (AO/ASIF)
- Baker's cyst: etiopathogenesis and clinical presentation
- Algorithm for choosing osteosynthesis in distal femur fractures
Master the entire topic in the "Traumatology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Knee dislocations" and 812 other subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 35 video lessons on the subject
Other topics in the "Specialized Adult Traumatology" section
The entire "Specialized Adult Traumatology" sectionPrepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.