ACL Reconstruction

ACL reconstruction is a surgical procedure that replaces a torn anterior cruciate ligament (ACL) — one of the main stabilising ligaments inside the knee — with a new graft so the knee can function normally again.

The ACL runs diagonally through the centre of the knee and stops the shin bone from sliding forward in front of the thigh bone. When it tears, the knee becomes unstable and gives way, especially during twisting or cutting movements. Because the ACL has very little ability to heal on its own, surgeons replace it with a piece of tendon taken from the patient's own body (an autograft) or from a donor (an allograft). The new tendon is threaded through small tunnels drilled in the bones and fixed in place, then gradually bonds to the bone over several months.

ACL reconstruction is considered when a torn ACL causes persistent knee instability that limits daily activities or sport, and when non-surgical treatment such as physiotherapy has not restored enough function.

• Complete or near-complete ACL tear confirmed by MRI (magnetic resonance imaging) and clinical examination.
• Recurrent episodes of the knee 'giving way' during everyday activities such as walking on uneven ground or climbing stairs.
• Active athletes, or anyone whose work or lifestyle demands a stable, pivoting knee.
• ACL tear combined with damage to other structures in the same knee, such as the meniscus (the cushioning cartilage) or other ligaments.
• Young patients with open growth plates, assessed on an individual basis by a specialist.

ACL reconstruction may not be the right choice in every situation. Doctors typically advise against or delay surgery when:

• The knee still has significant swelling and very limited movement — surgery usually waits until full range of motion is regained.
• The patient is older, less active, and the knee is stable enough for daily life without surgery.
• There is a serious active infection anywhere in the body.
• Severe osteoarthritis (joint cartilage worn away) is already present in the same knee.
• The patient cannot commit to the long rehabilitation programme after surgery.

ACL reconstruction is a well-established procedure, but like any surgery it carries recognised risks that the surgical team will discuss with the patient beforehand.

• Knee pain and swelling in the weeks after surgery — very common and expected as part of healing.
• Stiffness or reduced range of motion if rehabilitation exercises are not followed closely.
• Graft failure — the new tendon does not fully bond to the bone, or re-tears, particularly if the knee is loaded too early.
• Infection at the incision sites or inside the joint (septic arthritis — infection spreading into the joint space).
• Bleeding inside the knee joint (haemarthrosis), which may require drainage.
• Numbness or altered sensation around the knee, usually from a small skin nerve disturbed during surgery.
• Blood clot in a leg vein (deep vein thrombosis), which in rare cases can travel to the lungs.
• Donor-site discomfort — aching or weakness at the area where the graft tendon was harvested from the patient's own body.
• Anaesthesia-related reactions, managed by the anaesthetics team.
• In the long term, a higher chance of developing early knee osteoarthritis compared with a knee that was never injured.

Preparing well for ACL reconstruction helps reduce the risk of complications and gives the new graft the best chance of healing. Preparation covers what the patient does in the days and weeks before surgery, the tests that are usually carried out, and what happens on the day.

Before the procedure, the surgical team will typically ask the patient to:

• Stop eating and drinking (fast) for a set number of hours before the operation — the exact time will be confirmed by the hospital, as it depends on the type of anaesthesia planned.
• Pause or adjust certain medications, especially blood thinners and anti-inflammatory painkillers, for a period agreed with the doctor.
• Stop smoking as early as possible before surgery, since smoking slows bone and tendon healing and raises infection risk.
• Avoid alcohol for at least several days before the procedure.
• Complete a course of pre-operative physiotherapy ('prehabilitation') to strengthen the muscles around the knee and regain full range of motion before surgery — this is strongly linked to better outcomes.
• Arrange for someone to drive them home after discharge and stay with them for the first day or two.
• Prepare the home for limited mobility: crutches, a raised toilet seat if needed, ice packs, and easy access to a sleeping area on the ground floor if possible.

Tests that are usually ordered before surgery include blood tests to check general health and clotting, and sometimes an electrocardiogram (ECG — a recording of the heart's electrical activity) if the patient is older or has heart concerns. The MRI scan taken earlier to diagnose the tear is reviewed again by the surgeon to plan the exact approach.

On the day of surgery, the procedure generally follows these steps:

• 1. The patient is admitted, identity and consent forms are confirmed, and the surgical site is marked.
• 2. The anaesthetist (doctor who manages pain and consciousness during surgery) gives either general anaesthesia (the patient is fully asleep) or regional anaesthesia (the lower body is numbed), depending on the plan agreed in advance.
• 3. The surgeon makes small incisions (cuts) around the knee to insert an arthroscope (a thin tube with a camera) — this is called arthroscopic, or keyhole, surgery.
• 4. The torn ACL remnants are removed and the inside of the joint is inspected. Any damage to the meniscus or other structures is treated at the same time if needed.
• 5. The graft tendon is harvested — taken from the patient's own knee tendons (commonly the patella tendon or hamstring tendon) or, if an allograft is used, prepared from donor tissue.
• 6. Small tunnels are drilled through the shin bone and thigh bone at exactly the positions where the original ACL was attached.
• 7. The graft is threaded through the tunnels and fixed securely at both ends with specialised fixation devices (screws or other implants).
• 8. The incisions are closed with sutures (stitches) or staples, and a sterile dressing is applied.
• 9. The patient is moved to the recovery area to wake from anaesthesia under nursing observation.

Recovery from ACL reconstruction is a gradual process that usually takes many months. The new graft does not simply replace the old ligament overnight — it goes through a biological process called ligamentisation, where the body slowly converts the tendon tissue into functioning ligament tissue. Rushing this process by returning to sport too early is one of the most common reasons for graft failure.

• Most patients go home on the same day as surgery or after one night in hospital, depending on the hospital's protocol and how the patient recovers from anaesthesia.
• Crutches are usually needed for the first week or two to avoid putting full weight on the operated leg — the physiotherapist will advise when it is safe to walk without them.
• Ice packs and keeping the leg elevated (raised above the level of the heart) help control swelling and pain in the first few days.
• A structured physiotherapy (rehabilitation) programme typically begins within days of surgery and continues for many months — this is the most important part of recovery.
• The wound dressing is usually changed and the incision sites checked at a follow-up appointment within the first week or two after surgery.
• Stitches or staples are removed at the appropriate time as directed by the surgical team.
• Driving is not permitted until the operated leg can react quickly and safely — the doctor will confirm when this is allowed.
• Return to desk work or light daily activities can often happen within a few weeks, while return to pivoting sports (football, basketball, badminton) typically takes many months and is guided by both time and objective tests of strength and stability.
• Long-term lifestyle advice usually includes maintaining healthy body weight to protect the knee, continuing strength and balance exercises, and warming up properly before physical activity.
• Follow-up appointments continue at intervals set by the surgeon to monitor graft maturation and overall knee health.