ACL Reconstruction

Introduction

If you have been told you have a torn anterior cruciate ligament (ACL) and surgery is being discussed, you are probably weighing a lot of questions at once. How is the operation done? Which graft is used? How long until you can walk normally, drive, work, or return to sport? What does rehabilitation actually involve, and what are the realistic chances of getting back to the activities you care about?

This guide is written for people who already have an ACL tear and are planning the next phase of care. It walks through what ACL reconstruction is, who tends to benefit from it, what alternatives exist, how the surgery is performed, and — in detail — what recovery looks like over the months that follow. It also covers risks, the special situation of children and adolescents, and the long-term outlook for the knee.

ACL reconstruction is one of the most studied and most refined operations in orthopaedic sports medicine. The surgery itself is now usually a same-day arthroscopic procedure. The bigger story is the rehabilitation that follows, which typically lasts nine to twelve months and is the single most important factor in how well the knee performs in the long run.

What Is ACL Reconstruction?

The anterior cruciate ligament, or ACL, is one of four main ligaments that hold the knee joint together. It runs diagonally through the middle of the knee, connecting the thigh bone (femur) to the shin bone (tibia). Its main job is to stop the tibia from sliding forward on the femur and to control rotational movements — the twisting and pivoting that happens during cutting, pivoting, jumping, and changing direction.

When the ACL tears completely, it does not heal on its own. The two ends retract and the tissue does not reattach in a way that restores function. The knee may feel stable when walking in a straight line, but it tends to give way during twisting or pivoting movements. This instability can damage the meniscus and the joint cartilage over time.

ACL reconstruction is a surgical procedure in which the torn ligament is replaced with a new piece of tendon, called a graft. The graft is passed through small tunnels drilled into the thigh bone and shin bone, and fixed in place so that it functions as a new ACL. Over the following months, the body remodels the graft so that it behaves more and more like a true ligament.

Reconstruction is different from repair. A repair stitches the torn ends back together. While there is renewed interest in primary ACL repair for certain very specific tear patterns in carefully selected patients, reconstruction with a graft remains the standard approach in current orthopaedic practice for most complete ACL tears.

Why Is ACL Reconstruction Performed?

The goal of ACL reconstruction is to restore stability to the knee so that it does not buckle or give way during activity. Stability matters for two reasons: it allows people to return to sports and physically demanding work, and it protects the other structures inside the knee — the menisci and the cartilage — from the repeated damage that an unstable knee causes.

Doctors commonly consider reconstruction when one or more of the following applies:

• The knee gives way during normal activities such as walking on uneven ground, going down stairs, or turning
• The person is young and physically active and wants to return to sports involving cutting, pivoting, or jumping
• The ACL tear is combined with a meniscus tear or other ligament injury that itself needs surgery
• The person’s work or lifestyle places repeated rotational demands on the knee
• A trial of physiotherapy has not restored enough stability for the activities the person needs to do

The American Academy of Orthopaedic Surgeons (AAOS) clinical practice guideline for ACL injuries notes that reconstruction is generally favoured in active patients and in those with combined injuries, where ongoing instability would risk further damage to the joint. The decision is always individual and weighs age, activity level, the condition of the rest of the knee, and the person’s own goals.

Who Is a Candidate?

Most people with a complete ACL tear can be considered for reconstruction, but the strength of the indication varies. Surgeons typically discuss candidacy in terms of three factors: the demands the person places on the knee, the condition of the knee itself, and overall health.

Activity demands

People who participate in pivoting sports — football, basketball, skiing, tennis, kabaddi, hockey, martial arts — or who do physically demanding work that involves twisting on a planted foot are often considered good candidates. So are people who simply experience repeated giving-way episodes during daily life.

Condition of the knee

An ACL tear is often accompanied by other injuries: meniscus tears, cartilage damage, bone bruising, or injury to other ligaments such as the medial collateral ligament. When these are present, reconstruction is often combined with treatment of the associated injury at the same operation. The presence of significant pre-existing arthritis may change the conversation, as the operation works best in knees that are otherwise healthy.

General health and readiness for rehabilitation

The operation itself is well tolerated by most adults. The bigger question is readiness for the rehabilitation programme that follows. A successful outcome depends heavily on consistent physiotherapy over many months. People who can commit to this, and who can manage the period of restricted activity early on, tend to do best.

Skeletally immature children and adolescents whose growth plates are still open are a special group and are covered in a dedicated section later in this article.

Alternatives to ACL Reconstruction

Not every ACL tear needs surgery. The decision to operate, to manage non-operatively, or to delay surgery is one of the most important conversations to have with your orthopaedic surgeon. A structured trial of non-surgical management is reasonable for some people, and for others it is the preferred path.

Structured physiotherapy and activity modification

Non-surgical management centres on a focused rehabilitation programme: progressive strengthening of the quadriceps, hamstrings, and hip muscles; neuromuscular training to improve how the knee controls itself during movement; and gradual return to activity within tolerance. People who do best with this approach typically have:

• Lower activity demands, particularly little need for cutting or pivoting sports
• A knee that feels stable in daily life after the initial swelling settles
• Partial rather than complete ACL tears, in some cases
• No meniscus or cartilage injury that itself requires surgery

Bracing

A functional knee brace can be used during sports or work activities to provide additional support. Bracing does not heal the ACL but can give some people more confidence and stability during specific activities. It is sometimes used as part of non-surgical management, and sometimes used after a return to sport following reconstruction.

Delayed reconstruction

Some people choose to try non-surgical management first and proceed to surgery only if the knee remains unstable. This “copers versus non-copers” framing is well described in the orthopaedic literature: copers manage their activities well without an intact ACL, while non-copers continue to have instability. A trial period of rehabilitation can help distinguish between the two.

Primary ACL repair

For a small subset of tears — typically proximal tears where the ligament has pulled off the femoral attachment — primary repair (stitching the ligament back) is being studied and offered at some centres. Current professional guidance considers this an option only in carefully selected cases. Reconstruction with a graft remains the standard approach for most complete ACL tears.

Whether non-surgical management, reconstruction, or another approach is appropriate is a clinical decision made together with your surgeon, based on the specific tear pattern, associated injuries, your activity goals, and how the knee behaves after the initial injury settles.

Surgical Approaches and Graft Choices

ACL reconstruction today is almost always performed arthroscopically — through small incisions, using a thin camera and slender instruments. The big decisions within the operation are the choice of graft and certain technical details about how the graft is positioned and fixed.

Arthroscopic ACL reconstruction

This is the standard technique. The surgeon makes two or three small incisions around the knee (each typically less than a centimetre), inserts a camera through one and small instruments through the others, and works inside the joint. The torn ACL is cleaned out, tunnels are drilled into the femur and tibia, the graft is passed through these tunnels, and the graft is fixed at both ends. Compared with traditional open surgery, arthroscopy means less soft tissue disruption, less postoperative pain, and earlier mobilisation.

Open ACL reconstruction

Open surgery, in which the knee joint is opened through a larger incision, is rarely performed today for primary ACL reconstruction. It may have a role in complex revision cases or where multiple ligaments need to be addressed at the same time.

Robotic-assisted and computer-navigated techniques

Some centres use computer navigation or robotic assistance to help plan tunnel placement with millimetre-level precision. These technologies are an aid to the surgeon, not a replacement for surgical judgment, and they are not universally available. The functional outcomes are similar to those of well-performed conventional arthroscopic reconstruction in most published studies.

Graft choices

The graft is the new ligament. Surgeons choose between several options, and the choice is one of the most discussed elements of the procedure.

Autograft uses tendon from the patient’s own body. The three commonly used autografts are:

• Hamstring tendon graft. Two of the hamstring tendons (semitendinosus, sometimes with gracilis) are harvested from the back of the thigh and folded to make a strong, multi-strand graft. This is one of the most widely used grafts worldwide. The harvest site usually heals without long-term functional problems for most people, though some loss of deep knee flexion strength can occur.
• Bone-patellar tendon-bone (BPTB) graft. A strip of the patellar tendon is taken with a small block of bone at each end. The bone blocks heal into the bone tunnels, providing very secure early fixation. BPTB grafts are often favoured for high-demand athletes. Some people experience kneeling pain or anterior knee discomfort afterwards.
• Quadriceps tendon graft. A strip of the quadriceps tendon, sometimes with a small bone block from the kneecap, is used. Interest in this graft has grown in recent years because of strong biomechanical properties and a relatively well-tolerated harvest.

Allograft uses tendon from a donor. Allografts avoid harvesting tendon from the patient and can be useful in older patients, in revision cases, or when multiple ligaments are being reconstructed at once. In younger, more active patients, several studies have suggested somewhat higher re-tear rates with allograft compared to autograft, and many surgeons reserve allograft for specific situations.

Synthetic grafts have been studied over the years but are not in widespread current use for primary reconstruction.

The choice of graft is individual. Major orthopaedic societies describe each of the common autografts as reasonable options, with the decision based on the patient’s age, sport, body habitus, surgeon experience with each graft, and shared discussion.

Preparing for ACL Reconstruction

Preparation for ACL reconstruction often begins weeks before the operation. The aim is to enter surgery with the best possible knee: minimal swelling, good range of motion, and reasonable quadriceps strength. This is sometimes called “prehabilitation” or “prehab”, and the evidence supporting it is now well established.

Prehabilitation

A short course of physiotherapy before surgery helps to:

• Reduce knee swelling
• Restore full or near-full knee extension and flexion
• Rebuild some quadriceps strength, which is often dramatically lost after injury
• Familiarise you with the exercises you will be doing after surgery

Going into surgery with a stiff, swollen knee makes early recovery harder and increases the risk of stiffness afterwards. Many surgeons prefer to delay reconstruction until the knee has “quietened down” from the initial injury.

Medical assessment

Before surgery, you will typically have:

• A review of your medical history, medications, and allergies
• Blood tests and, when needed, an ECG and chest evaluation
• A discussion with the anaesthesia team
• A review of your most recent MRI and any other imaging

Practical preparation

Before the day of surgery, it helps to:

• Arrange the home environment for a few weeks of limited mobility — a place to sleep on the ground floor if you have stairs, a chair with arms for getting up easily, a shower stool if available
• Plan for someone to help you for the first few days
• Stop smoking if you smoke. Smoking impairs graft healing and tissue recovery
• Follow fasting instructions from your anaesthesia team
• Pack loose clothing that can fit over a bulky knee dressing

What Happens During ACL Reconstruction

On the day of surgery, you will be admitted to the hospital or surgical centre, often for same-day discharge or a single overnight stay. The operation typically takes between one and two hours, depending on whether additional procedures such as meniscus repair are being done at the same time.

Anaesthesia

ACL reconstruction is usually performed under general anaesthesia, sometimes combined with a regional nerve block (such as a femoral or adductor canal block) that numbs the leg for several hours afterwards and reduces postoperative pain. Some centres use spinal anaesthesia. The anaesthesia plan is decided with the anaesthesia team based on your preferences and health.

The operation, step by step

1. Diagnostic arthroscopy. The surgeon first inspects the inside of the knee with the camera, confirming the ACL tear and looking for meniscus tears, cartilage damage, or other injuries.
2. Treatment of associated injuries. If there is a meniscus tear that can be repaired, this is often done first. Meniscus tears that cannot be repaired may be trimmed.
3. Graft harvest (for autografts). The chosen tendon is harvested through a small incision near the knee, prepared on a side table, and sized.
4. Removing the torn ACL. The remnants of the torn ligament are cleared from the joint to make space for the new graft.
5. Creating the bone tunnels. Tunnels are drilled into the femur and tibia at the natural attachment points of the ACL, using guides to position them precisely.
6. Passing and fixing the graft. The graft is passed through the tunnels and fixed at both ends, commonly using interference screws, suspensory buttons, or a combination of fixation devices.
7. Final check and closure. The surgeon tests the graft for appropriate tension and confirms that the knee moves through a full range without impingement. The small incisions are closed and a sterile dressing is applied.

You wake up in the recovery area with the knee bandaged and often in a brace. Pain control begins immediately, with a combination of nerve block effect, oral medication, and ice.

Recovery and Rehabilitation

Recovery from ACL reconstruction is a long, structured process. The surgery itself is one day. The rehabilitation that follows typically takes nine to twelve months, sometimes longer, and is the single most important determinant of how the knee will perform in the long run. Skipping or rushing rehabilitation is a leading reason for poor outcomes and re-injury.

The first two weeks

The early days focus on protecting the graft, controlling pain and swelling, and beginning gentle motion.

• You will use crutches and often a knee brace. Weight-bearing instructions depend on the surgeon and whether a meniscus was repaired
• Pain is managed with a combination of medications, ice, and elevation
• Gentle exercises begin almost immediately: ankle pumps, quadriceps activation (“quad sets”), straight leg raises, and gentle knee bending
• Achieving full knee extension — the ability to straighten the knee completely — is a priority from day one. Losing extension early is hard to recover later
• Wound care: dressings are usually changed at the first follow-up visit, and showering may be permitted once the wounds are sealed, typically within a week or two

Weeks three to six

The focus shifts to restoring motion, regaining quadriceps control, and beginning to walk normally.

• Most people gradually come off crutches during this period, depending on the surgical plan
• Physiotherapy intensifies, with stationary cycling, closed-chain exercises (such as mini-squats and step-ups), and progressive strengthening
• Range of motion typically reaches close to normal by the end of this period
• Driving may become possible toward the end of this phase, particularly for the left knee with an automatic vehicle, and later for the right knee. Your surgeon will guide you

Weeks six to twelve

By around six weeks, the knee usually feels much more functional in daily life. Rehabilitation now targets strength, balance, and the foundations of athletic movement.

• Strengthening progresses to include leg press, lunges, and more challenging closed-chain exercises
• Balance and proprioception (the knee’s sense of position) are trained with single-leg stance work and unstable surface exercises
• Low-impact cardio such as cycling and elliptical training is built up
• Light jogging in a straight line may be introduced toward the end of this period, depending on quadriceps strength and the surgical team’s protocol

Three to six months

The graft is biologically remodelling during this period — a process called “ligamentisation” — and it is mechanically weaker than it will eventually become. Rehabilitation continues to build strength and progresses toward sport-specific movement.

• Heavier strengthening is layered in
• Plyometric (jumping) drills are introduced gradually and with attention to landing mechanics
• Agility drills — change of direction, cutting movements — are added in a controlled way
• Sport-specific drills begin under supervision

Six to twelve months: return to sport

Return to pivoting sports is not based on the calendar alone. Current professional guidance, including consensus statements from sports medicine societies, emphasises that return-to-sport decisions should be based on objective criteria as well as time since surgery. These criteria typically include:

• Quadriceps and hamstring strength close to that of the uninjured leg (often measured as a percentage)
• Performance on hop tests and other functional measures
• Confidence in the knee and absence of giving-way episodes
• Completion of progressive return-to-sport drills

Light, non-pivoting activity is often possible around six months. Return to competitive pivoting sports typically occurs at nine to twelve months, and sometimes later. Returning too early is associated with a higher risk of graft re-injury, particularly in younger athletes. Many surgeons and physiotherapists now favour the later end of this window for young athletes returning to high-risk sports.

Risks and Complications

ACL reconstruction is generally a safe operation, but as with any surgery, complications can occur. Understanding them helps with realistic expectations and recognising problems early.

Common, usually manageable issues

• Swelling and bruising around the knee for several weeks
• Pain that gradually settles with medication, ice, and activity modification
• Numbness over a small area of skin near the incisions, particularly with hamstring or patellar tendon harvest
• Stiffness — difficulty regaining full motion. This is a leading cause of poor outcomes and is one reason early physiotherapy is so important

Less common but important complications

• Infection. Deep joint infection is uncommon after arthroscopic surgery but is serious when it occurs and usually requires antibiotics and sometimes further surgery
• Blood clots in the leg (deep vein thrombosis) or lungs (pulmonary embolism). Early mobilisation reduces this risk. Warning signs include calf pain or swelling, chest pain, or sudden shortness of breath
• Graft failure or re-tear. The new ligament can tear again, particularly during return to high-risk sports. Re-tear risk is highest in younger athletes who return to pivoting sports
• Persistent pain around the kneecap, sometimes related to graft harvest site or to changes in patellar tracking
• Loss of motion requiring further intervention, occasionally including a manipulation under anaesthesia or arthroscopic release
• Anaesthesia-related complications, which are uncommon in otherwise healthy patients

Long-term concerns

The risk of knee osteoarthritis later in life is higher after an ACL injury than in a knee that was never injured, whether or not reconstruction is performed. Reconstruction can help by restoring stability and protecting the menisci, but it does not eliminate the long-term risk entirely. Maintaining a healthy weight, ongoing strength training, and protecting the knee from further injury all matter.

Life After ACL Reconstruction

For most people who complete a structured rehabilitation programme, the knee feels stable, strong, and capable of supporting an active lifestyle. The long-term outlook is generally good, with most patients regaining a stable knee and returning to the activities that matter to them. A meaningful proportion of competitive athletes return to their pre-injury sport, though not every athlete reaches the same level as before.

Ongoing strength and movement training

The end of formal physiotherapy is not the end of taking care of the knee. Continuing strength training, balance work, and good movement patterns — particularly safe landing and cutting technique — reduces the risk of re-injury and helps the knee perform well over the long term. Neuromuscular training programmes designed to prevent ACL injury have been shown to reduce injury risk in young athletes and are useful both for the operated knee and for protecting the other knee.

Protecting the other knee

People who have torn one ACL have a meaningfully higher risk of tearing the ACL in the opposite knee later, particularly in younger athletes. Ongoing strength and neuromuscular training benefits both knees.

Long-term joint health

Maintaining a healthy weight, staying active without overloading the joint, and addressing any associated meniscus or cartilage issues all support long-term knee health. Regular follow-up with the orthopaedic team is appropriate if symptoms develop.

ACL Reconstruction in Children and Adolescents

ACL injuries in children and adolescents are increasingly common as more young people participate in organised sport. Surgical decisions in skeletally immature patients — those whose growth plates have not yet closed — require special consideration.

• All-epiphyseal techniques, in which the tunnels avoid the growth plates entirely
• Partial transphyseal techniques, which minimise the disturbance to the growth plate
• Iliotibial band reconstruction (extra-articular techniques), which use tissue from outside the joint to provide stability without crossing the growth plates

Delaying surgery until skeletal maturity used to be a common approach but is now generally not favoured for active children, because ongoing instability in a young, active knee tends to cause meniscus tears and cartilage damage that compromise long-term joint health. Current consensus among paediatric sports medicine societies favours early surgical stabilisation using age-appropriate techniques in children with complete ACL tears who are active.

The rehabilitation principles in young patients are similar to adults but with attention to age-appropriate strength training, monitoring of growth, and a particularly cautious approach to return to pivoting sports given the high re-injury risk in young athletes.

Frequently Asked Questions

How is ACL reconstruction different from ACL repair?

Reconstruction replaces the torn ligament with a graft of tendon. Repair stitches the torn ends back together. Reconstruction is the standard approach for most complete ACL tears. Primary repair is being studied for specific tear patterns but is not the standard.

How painful is ACL reconstruction?

Most people describe the first few days as uncomfortable but manageable, particularly when a nerve block is used for the first day or two and medications are taken as prescribed. Pain typically improves substantially over the first one to two weeks. Discomfort at the graft harvest site can persist longer in some people.

How long will I need crutches?

Most people use crutches for one to three weeks. The exact timing depends on the surgical plan and whether a meniscus repair was done at the same time, which can require a longer period of restricted weight-bearing.

When can I drive again?

For the left knee in an automatic vehicle, driving is often possible within two to three weeks once you are off strong pain medication and feel safe controlling the vehicle. For the right knee, or with a manual vehicle, it usually takes longer — often four to six weeks or more. Your surgeon and physiotherapist will guide this decision.

When can I return to work?

Office-based work can often be resumed within one to two weeks, sometimes with adjustments to allow leg elevation. Work that involves standing, walking long distances, or physical labour requires longer — commonly six weeks to three months depending on the demands.

Which graft is best?

There is no single best graft for everyone. Hamstring, bone-patellar tendon-bone, and quadriceps tendon autografts are all considered reasonable options by major orthopaedic societies, each with different trade-offs. Surgeons usually recommend a graft based on the patient’s age, activity goals, body type, the surgeon’s own experience, and the patient’s preferences after discussion.

Will I be able to return to my sport?

Many people do return to sport after ACL reconstruction, including to pivoting sports. The likelihood depends on factors including age, the sport, completion of rehabilitation, and meeting return-to-sport criteria. Return to competitive sport typically occurs between nine and twelve months after surgery, sometimes later. Returning too early increases the risk of re-injury.

How long does the graft last?

Once the graft has healed and remodelled, it can function for many years and often for life. The main long-term risk is a fresh injury that tears the graft, particularly during high-risk sport. The graft does not wear out in the way a joint replacement might.

What should I look for when choosing a surgeon?

Useful things to consider include the surgeon’s experience with ACL reconstruction specifically (rather than orthopaedic surgery in general), familiarity with the graft type you are considering, experience with associated injuries such as meniscus repair, and the structure of the rehabilitation programme they work with. Meeting the surgeon and feeling able to ask questions matters as well.

Can I avoid surgery altogether?

Some people with ACL tears manage well without surgery through structured physiotherapy and activity modification, particularly those with lower activity demands or partial tears. Whether this is appropriate is a clinical decision based on the tear, the rest of the knee, and the demands you place on it. A trial of non-surgical management is reasonable for many people before deciding on surgery.

Conclusion

ACL reconstruction is a well-established operation that, for the right person, restores stability to a knee that would otherwise tend to give way. The surgery itself is now usually a same-day arthroscopic procedure, but the larger investment is the rehabilitation programme that follows — typically nine to twelve months of structured physiotherapy, strength work, and progressive return to activity.

The decisions along the way — whether to operate at all, which graft to use, when to return to sport — are clinical decisions made in conversation with your surgeon and rehabilitation team, taking into account your specific injury, the rest of your knee, your activity goals, and your readiness to commit to the rehabilitation process. Understanding what the operation involves, what recovery looks like, and what realistic outcomes are makes that conversation more productive and helps you plan the months ahead.