A knee dislocation, formally known as a tibiofemoral dislocation, is a severe injury where the femur (thigh bone) and the tibia (shin bone) completely separate. This rare event typically requires immense force, such as a high-speed motor vehicle collision or a significant fall. The injury must be treated as a limb-threatening medical emergency due to the high probability of damage to the blood vessels and nerves passing through the knee area. Immediate professional medical attention is necessary to prevent potential long-term complications, including limb loss.
Emergency Response and Vascular Assessment
The initial priority upon arrival at the emergency room is a neurovascular assessment of the injured leg. This examination determines the status of blood flow and nerve function below the knee. The popliteal artery is tightly tethered behind the joint and is easily stretched or torn during dislocation, resulting in injury in 20 to 40 percent of cases.
To check the vascular status, a physician measures the Ankle-Brachial Index (ABI), which compares blood pressure in the ankle to the arm. An ABI reading below 0.9 suggests compromised blood flow and requires urgent further investigation, such as a CT angiogram, or immediate surgical exploration. Even if a pulse is palpable, popliteal artery injury may still be present, so serial examinations monitor for delayed signs of vascular compromise.
Nerve damage is a concurrent concern, most commonly affecting the common peroneal nerve, which controls sensation and movement in the foot. Damage to this nerve is observed in about 25 percent of these injuries, potentially leading to “foot drop” where the patient cannot lift the front part of their foot. Furthermore, the trauma and swelling can lead to compartment syndrome, a serious condition where pressure builds up within the muscles. This pressure can quickly cut off blood flow and requires an emergency surgical release.
Closed Reduction and Immediate Joint Stabilization
If the knee remains dislocated upon hospital arrival, the limb must be realigned immediately through a procedure known as closed reduction. This is often performed under procedural sedation or general anesthesia to manage pain and relax the surrounding thigh muscles. Reduction is urgent if there is evidence of vascular compromise, as realigning the bones may relieve pressure on the damaged popliteal artery.
The technique involves specific, controlled manipulation, usually starting with gentle, sustained longitudinal traction applied to the lower leg. For an anterior dislocation (tibia moved forward), the surgeon applies downward pressure to the thigh while lifting the tibia forward. Conversely, a posterior dislocation (tibia moved backward) requires the surgeon to lift the tibia anteriorly to guide it back into place.
After reduction, the neurovascular status must be immediately re-assessed to confirm blood flow has been restored or maintained. Post-reduction imaging, typically X-rays, verifies proper joint alignment and checks for associated fractures. The knee is then placed in a temporary long-leg splint or brace to protect the joint from further instability as definitive care is prepared. In cases of severe instability or vascular repair, the joint may be stabilized with a temporary external fixator, which uses pins connected to an external frame.
Surgical Intervention for Ligament and Soft Tissue Repair
A knee dislocation involves the rupture of at least two, and often three or four, major stabilizing ligaments, including the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and the collateral ligaments (MCL and LCL). Because of this multi-ligament damage, surgical reconstruction is almost always necessary to restore long-term stability and function. Surgeons reconstruct the torn ligaments using grafts, often taken from the patient’s own tendons (autograft) or from a donor (allograft).
The timing of the surgery depends on the patient’s overall health and the condition of the injured soft tissues. Many surgeons delay the definitive multi-ligament reconstruction for one to three weeks after the initial injury. This delay allows severe swelling and inflammation to subside, reducing the risk of post-operative stiffness, which is a common complication known as arthrofibrosis.
During the procedure, the surgeon addresses all damaged structures, which may include repairing meniscal tears or damaged cartilage surfaces. Reconstruction often involves a combination of arthroscopic techniques, using small incisions and a camera, and open surgical approaches, particularly for the collateral ligaments. The goal is to place the new ligament grafts precisely to recreate the knee’s anatomical balance.
Comprehensive Rehabilitation and Recovery Timeline
Recovery from a knee dislocation and multi-ligament reconstruction typically spans nine to twelve months, or sometimes longer. The initial phase of rehabilitation focuses on protected healing, managing pain and swelling, and restoring a limited range of motion. A specialized, hinged knee brace is frequently used to protect the reconstructed ligaments while allowing controlled movement within a prescribed range.
Physical therapy begins with passive range-of-motion exercises to prevent stiffness and scar tissue formation. The patient is often non-weight-bearing for the first four to six weeks, relying on crutches or a walker. Progression to partial and then full weight-bearing is controlled to avoid excessive strain on the healing ligament grafts.
As healing advances, the focus shifts to strengthening the muscles surrounding the knee, particularly the quadriceps and hamstrings, which aid dynamic joint stability. Later phases involve functional training, including balance work, agility drills, and sport-specific movements, to prepare the patient for a return to full activity. Patient adherence to this long-term rehabilitation protocol is a significant determinant of the final outcome, influencing the chances of returning to pre-injury activity levels.