Overview
The anterior cruciate ligament (ACL) runs diagonally inside the knee joint, from the back of the femur (femur) to the front of the tibia (tibia). It crosses the posterior cruciate ligament at the center of the knee. The ACL is the main restraint that keeps the tibia from sliding forward and the knee from pivoting out of control. Those are exactly the forces of cutting, planting, and landing in sport. The ACL does not heal reliably after a complete tear. It lacks a good blood supply, and the joint fluid washes away the clot that would normally bridge healing tissue. Reconstruction replaces the torn ligament with a tendon graft, which remodels into ligament-like tissue over the following months. A torn ACL leaves the knee unstable for pivoting activity. Left alone, each episode of giving way adds damage to the menisci and cartilage. That damage speeds up arthritis over the long term.
How the Procedure Works
The first decision is what tissue to use as the new ligament, the graft. There are three good options. A strip from the patellar tendon below the kneecap heals fastest, because it carries bone on both ends. Tendons from the hamstrings are a reliable alternative when we want to spare the front of the knee. A strip from the quadriceps tendon above the kneecap gives a thicker graft with modest impact at the donor site. Your surgeon picks the graft based on your sport, your anatomy, and your priorities.
Once the torn ACL is cleared out through the keyhole camera approach, the new graft is fed through tunnels drilled in the femur and tibia. It is placed at the exact spots where the original ligament used to attach. Tunnel position is the single most technique-sensitive step in the operation. Even a few millimeters off-center increases the chance of rotational instability and a re-tear. The graft is tensioned, locked at both ends, and stress-tested through the full arc of knee motion before closing. One thing to know: the graft isn't a working ligament on day one. It remodels into one over months of step-by-step loading. That is why how you pace rehab matters as much as how the surgery went.
When to Consider ACL Reconstruction
ACL reconstruction is generally offered when your symptoms, imaging, and your goals together point to surgery as the next step. The typical patient profile:
Active Patients Wishing to Return to Sport
Athletes who want to return to pivoting or cutting sports (soccer, basketball, skiing, football), where a stable ACL is non-negotiable.
Young Patients with a Long Active Life Ahead
Reconstruction protects the meniscus and cartilage from the repeated giving-way episodes of a knee without a working ACL.
Associated Injuries That Need Addressing
Meniscal tears, cartilage damage, or multi-ligament injury that should be surgically managed in the same operation.
Treats: ACL Tear
Risks & Why We Still Recommend It
Every operation carries risk. This procedure is offered because the condition, when left untreated, can cause repeated giving-way episodes that damage the meniscus and cartilage and bring a permanent end to pivoting sports. 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 ACL reconstruction include:
- bleeding and infection
- anesthesia risk
- graft-site pain (patellar or hamstring) that usually settles
- stiffness or trouble fully straightening the knee
- graft re-tear, especially with early return to cutting sport
- blood clot in the leg or lung
- rarely, injury to nearby nerves or vessels
We proceed when the exam and MRI confirm an unstable knee and you want to return to pivoting activity. Patients who don't need this operation don't get it.
Frequently Asked
questions we hear in clinicWhy won't my ACL heal on its own?
The ACL lacks a good blood supply, and the joint fluid washes away the clot that would normally bridge healing tissue. That is why a complete tear does not heal reliably and why reconstruction replaces the torn ligament with a tendon graft.
Which graft is best?
There are three good options. A strip from the patellar tendon heals fastest, because it carries bone on both ends. Hamstring tendons are a reliable alternative when we want to spare the front of the knee. A strip from the quadriceps tendon gives a thicker graft with modest impact at the donor site. Your surgeon picks the graft based on your sport, your anatomy, and your priorities.
What happens if I skip surgery?
A torn ACL leaves the knee unstable for pivoting activity. Left alone, each episode of giving way adds damage to the menisci and cartilage, which speeds up arthritis over the long term, and it means a permanent end to pivoting sports.
Is the new ligament strong right away?
No. The graft is not a working ligament on day one. It remodels into one over months of step-by-step loading, which is why how you pace rehab matters as much as how the surgery went.
What makes the operation succeed or fail?
Tunnel position is the single most technique-sensitive step. Even a few millimeters off-center increases the chance of rotational instability and a re-tear. The graft is placed at the exact spots where the original ligament attached, then tensioned, locked at both ends, and stress-tested through the full arc of knee motion before closing.
What are the risks?
The risks we discuss include bleeding and infection, anesthesia risk, graft-site pain that usually settles, stiffness or trouble fully straightening the knee, graft re-tear (especially with early return to cutting sport), blood clot in the leg or lung, and rarely injury to nearby nerves or vessels.
Further Reading
External patient-education references and related OSI pages for additional background:
