Overview
A knee dislocation is a high-energy injury that tears two or more of the knee's major ligaments at once. The most common pair is the ACL and PCL together. When both are gone, the knee has lost its front-to-back and back-to-front restraints at the same time. The ligaments on the inner and outer sides of the knee are often torn as well. So is the posterolateral corner, a cluster of structures on the back-outer corner of the knee that controls rotation and side-to-side stability. The knee can partly slide back into place on its own before imaging. Because of that, the full severity is easy to underestimate at first.
Two problems demand attention right away, before any reconstruction is planned. First, the main artery behind the knee (the popliteal artery) can be injured in a dislocation. A missed artery injury can cost the limb. Second, the nerve that wraps around the outside of the knee and lifts the foot and toes (the peroneal nerve) can be stretched or torn. Both are checked urgently in the emergency setting.
Once the blood supply is confirmed safe and the soft tissue has calmed down, we plan surgery. We rebuild all the torn ligaments, often in a single operation. Without reconstruction, the knee cannot reliably bear weight or support normal walking. The cartilage surfaces also grind against each other in ways that speed up permanent joint damage.
How the Procedure Works
The first priority after a knee dislocation is checking the artery behind the knee; a missed injury can cost the limb. Once the blood supply is confirmed and the swelling allows, we plan the operation. Most cases are done in one sitting. We rebuild the PCL first to set a stable reference at the back of the knee, then the ACL, then the collateral or corner injuries. The order matters. Each new ligament is tensioned against the one before it. Getting it wrong produces a stiff or unstable knee.
Rebuilding four or more ligaments takes planning for graft tissue. We typically use a mix of your own tendon (autograft) and donor tissue (allograft). That way we do not harvest too much from your own tendons. Motion starts early after surgery. Stiffness is the most common problem after this operation. Rehab is a constant balance: protect the grafts, but keep the knee moving.
When to Consider Multi-Ligament Knee Reconstruction
We offer this surgery when the symptoms, the imaging, and a trial of non-operative care all point the same way. The typical picture includes:
Combined cruciate injury
ACL and PCL torn together, with or without collateral involvement.
Prior knee dislocation
A documented knee dislocation, even if it slid back into place before imaging.
Failure of conservative care
Less severe combinations where bracing and rehab have not produced a stable knee.
Conditions This Treats
Risks & Why We Still Recommend It
Every operation carries risk. This procedure is offered because the condition, when left untreated, can cause a grossly unstable knee that cannot reliably support standing or walking and steadily destroys its own cartilage. The decision to proceed weighs the risks of surgery against the limitations the condition places on daily function. Surgery does not remove risk; it addresses a problem that is otherwise progressive. Whether it is appropriate is determined for each patient in consultation with the surgeon.
The risks we discuss with you before multi-ligament knee reconstruction include:
- bleeding and infection
- anesthesia risk
- stiffness requiring manipulation
- graft re-tear or stretch-out
- instability that remains in one or more directions
- blood clot in the leg or lung
- injury to vessels or nerves (the work sits close to the artery and nerve described above)
Surgery makes sense for a knee with two or more torn ligaments and clear instability on exam and imaging. If the operation is not right for you, we will say so.
Frequently Asked
questions we hear in clinicMy knee popped back into place on its own. Could it still be serious?
Yes. The knee can partly slide back into place before imaging, so the full severity is easy to underestimate at first. A documented knee dislocation, even one that slid back in on its own, is one of the reasons we consider this reconstruction.
Why is this checked in the emergency room first?
Two problems demand attention right away, before any reconstruction is planned. The main artery behind the knee can be injured in a dislocation, and a missed artery injury can cost the limb. The nerve that wraps around the outside of the knee and lifts the foot and toes can be stretched or torn. Both are checked urgently.
Is everything fixed in one operation?
Most cases are done in one sitting. We rebuild the PCL first to set a stable reference at the back of the knee, then the ACL, then the collateral or corner injuries. The order matters, because each new ligament is tensioned against the one before it.
Where does the graft tissue come from?
Rebuilding four or more ligaments takes planning for graft tissue, so we typically use a mix of your own tendon (autograft) and donor tissue (allograft). That way we do not harvest too much from your own tendons.
What is the most common problem after surgery?
Stiffness. Motion starts early after surgery, and rehab is a constant balance: protect the grafts, but keep the knee moving.
Can bracing and rehab work instead of surgery?
Sometimes, for less severe combinations; surgery is offered when bracing and rehab have not produced a stable knee. Without reconstruction, a knee with two or more torn ligaments cannot reliably bear weight or support normal walking, and the cartilage surfaces grind in ways that speed up permanent joint damage.
Further Reading
External patient-education references and related OSI pages for additional background:
