Knee dislocation is a serious injury, usually caused by high-energy trauma. It is classically defined as complete loss of articular congruence between the femur and the tibia, confirmed by radiography. However it is common that the reduction happens spontaneously. For this reason, today the investigators also consider a patient suffered knee dislocation in the presence of multi-ligament injury involving the posterior cruciate ligament, often in association with anterior cruciate ligament, lateral and/or medial ligamentous complex.

It is considered a serious injury, because both the strong association with vascular and nerve damage, which can lead to the need for limb amputation, such as the difficulty in obtaining a good functional outcome even after treatment of all ligament injuries.

The treatment of these injuries aims to achieve knee stability. Joint mobility is often sacrificed in the postoperative period, with the use of immobilizations such as casts, splints or bracing. Unfavorable clinical outcomes with high rates of stiffness and joint pain are very common in these patients. In attempts to improve these results, rehabilitation protocols with early range of motion can be employed. However, results may remain unsatisfactory, predominantly because of knee instability recurrence.

Stannard and Zaffagnini proposed a new model for treatment of acute knee dislocations. In this model, after multi-ligament reconstruction or repair, a knee articulated external fixator is used. Such external fixator allows early and aggressive joint mobility in the sagittal plane only. Flexion and extension are permitted, but rotational movements, translations in the anterior-posterior plane, lateral (varus) and medial (valgus) openings are not allowed. Thus protective stability is ensured for ligament reconstruction procedures. Simultaneously the investigators allow immediate joint mobilization, reducing the risk of arthrofibrosis, joint stiffness and postoperative ligament laxity.

There is no consensus regarding the use of hinged external fixator postoperatively in multiple ligament reconstruction procedures for treatment of knee dislocations.

The objective of this study is comparing functional outcomes after ligament reconstruction in patients with knee dislocation, with or without the use of hinged external fixator.

Inclusion Criteria:

• adults aged between 18 and 50 years old, diagnosed with knee dislocation, classified as KD-III and KD-IV
• absence of knee arthritis in initial radiographs
• absence of systemic diseases or disorders of collagen altering bone quality
• absence of previous surgical interventions in the knee
• possibility of using medications
• maximum of three months of injury to treatment
• understanding and acceptance by the patient to participate

Exclusion Criteria:

• abandoning medical care
• inability to follow the treatment plan