ACL Surgery

Senior Consultant Orthopaedic Surgeon

Anterior Cruciate Ligament (ACL) surgery is a reconstructive procedure that repairs a torn ACL, one of the primary stabilising ligaments in the knee joint. The surgery involves removing the damaged ligament and replacing it with a tissue graft to create a new ligament. This procedure aims to restore knee stability and function, enabling patients to return to daily activities and sports after appropriate rehabilitation.

Indications for ACL Surgery

The following conditions may indicate that ACL surgery would benefit a patient experiencing knee instability or dysfunction.

A complete rupture of the anterior cruciate ligament typically requires surgical intervention. These tears impair knee stability, causing the knee to give way during activities.

Some partial tears affect knee function substantially enough to necessitate surgery. The degree of instability experienced during daily activities or sports helps determine if surgery is needed.

ACL tears occurring alongside damage to other knee ligaments, such as the MCL or PCL, often require surgical treatment. Multiple ligament injuries typically cause greater instability and functional impairment.

Patients who participate in sports or occupations that involve pivoting, cutting, or jumping motions generally benefit from ACL reconstruction. These activities place significant stress on the knee joint, requiring a stable ACL.

Surgery may be recommended when non-surgical approaches such as physical therapy and activity modification do not adequately improve symptoms. Persistent instability despite conservative management suggests the need for surgical intervention.

Benefits of ACL Surgery

ACL surgery offers several advantages for patients with significant ligament tears and knee instability that impact their quality of life. Key benefits include:

Restored Knee Stability

Surgery re-establishes the stabilising function of the ACL, preventing the knee from giving way during activities. The reconstructed ligament helps control rotational forces and forward movement of the tibia relative to the femur.

Return to Physical Activities

Most patients can resume sports and other demanding physical activities after surgery and rehabilitation. The reconstructed ACL allows for pivoting, cutting, and jumping movements necessary for many athletic endeavours.

Prevention of Secondary Injuries

Addressing ACL tears helps prevent additional knee injuries that can occur due to instability. Unstable knees risk meniscal tears, cartilage damage, and early-onset arthritis.

Long-Term Joint Preservation

ACL reconstruction can help reduce the risk of developing premature osteoarthritis in the knee. Restoring proper knee biomechanics distributes forces more evenly across the joint surfaces.

Improved Function for Daily Activities

Surgery enables patients to perform routine activities without the knee buckling or feeling unstable. Simple tasks like walking down stairs, squatting, or quickly changing direction become more manageable and comfortable.

Surgical Techniques

This method uses tissue from the patient’s own body to create the new ACL. The surgeon harvests a portion of the patellar tendon, hamstring tendons, or quadriceps tendon to form the graft. Autografts typically have high strength and integration with the body’s tissues. The harvested tissue is shaped and prepared to function as the new ligament before placement within the knee joint.

Allografts utilise donor tissue from a cadaver for ACL reconstruction. This approach eliminates the need for graft harvesting from the patient, potentially reducing surgical time and post-operative pain at the harvest site. The process still involves arthroscopic placement of the graft within tunnels created in the femur and tibia. Allografts may be preferred for older patients or those undergoing revision surgery.

Most modern ACL reconstructions are performed arthroscopically using small incisions and a camera system. The surgeon inserts a thin scope and specialised instruments through small portals around the knee. This minimally invasive technique allows for direct visualisation of the knee structures while minimising tissue trauma. The arthroscopic approach results in less post-operative pain and faster initial recovery compared to open surgery.

Single-bundle reconstruction replaces the ACL with one graft strand, while double-bundle techniques use two grafts to more closely mimic the natural ACL anatomy. The double-bundle approach attempts to reproduce both the anteromedial and posterolateral bundles of the native ligament. This technique may provide better rotational control but requires more surgical complexity and may not be suitable for all patients.

Preparing for Surgery

Medical Evaluation

A comprehensive assessment includes physical examination, imaging studies, and laboratory tests. The surgeon evaluates knee stability, range of motion, and associated injuries using clinical tests like the Lachman test. MRI scans confirm the ACL tear and identify other potential knee injuries that may require treatment during surgery.

Medication Adjustments

Certain medications must be stopped before surgery to reduce bleeding risks. Blood thinners, anti-inflammatory drugs, and some supplements should be discontinued according to medical advice. Patients should provide a complete list of all medications, vitamins, and supplements to their surgical team for specific guidance on timing of discontinuation.

Pre-operative Physical Therapy

A course of “prehabilitation” exercises helps optimise outcomes after surgery. These exercises focus on maintaining muscle strength, particularly in the quadriceps and hamstrings, and preserving range of motion. Better pre-operative knee function correlates with improved post-operative recovery and outcomes.

Lifestyle Modifications

Smoking cessation is advised, as tobacco use can impair healing and increase complication risks. Patients who smoke should attempt to quit at least two weeks before surgery. Maintaining a balanced diet and healthy weight supports healing and reduces surgical risks.

Step-by-Step Procedure

Anaesthesia Administration: The procedure begins with anaesthesia, which may be general, spinal, or regional. The anaesthesiologist discusses options based on the patient’s medical history and preferences.
Diagnostic Arthroscopy: The surgeon creates small incisions around the knee to insert the arthroscope and surgical instruments. This initial examination allows for assessment of the ACL tear and evaluation of other knee structures, including the menisci, cartilage surfaces, and other ligaments. Any additional damage discovered during this phase may be addressed during the same procedure.
Graft Harvesting: If using an autograft, the surgeon removes the selected tendon tissue. For hamstring grafts, small incisions on the inner aspect of the lower leg allow access to the semitendinosus and gracilis tendons. Patellar tendon grafts require an incision at the front of the knee to harvest a section of tendon with bone plugs from the kneecap and tibia. The harvested tissue is then prepared on a separate table while the knee arthroscopy continues.
Tunnel Creation: Small tunnels are drilled in the femur and tibia to position the graft in line with the original ACL. Placement is guided by anatomical landmarks or navigation systems to ensure proper alignment. Accurate positioning helps restore knee function and supports long-term graft durability.
Graft Placement and Fixation: The prepared graft is passed through the tunnels and secured at both ends using various fixation devices. These may include screws, buttons, or pins, depending on the graft type and surgeon preference. The fixation must be strong enough to hold the graft in place while allowing for biological incorporation of the tissue. Tension is carefully adjusted to provide stability while maintaining full range of motion.
Final Assessment and Closure: The surgeon tests the knee’s stability and the graft’s tension through a range of motion. Any necessary adjustments are made before the incisions are closed. The small arthroscopic incisions are typically closed with sutures or surgical tape, while graft harvest sites may require deeper closure techniques. A sterile dressing and compression bandage are applied to minimise swelling.

Post-Surgical Care and Recovery

Immediate Post-Operative Care: Pain is managed with medications, including nerve blocks from surgery. Swelling control involves elevation, compression, and ice packs. Gentle foot and ankle movements help prevent blood clots.
Early and Progressive Rehabilitation: Initial focus is on protecting the graft while regaining motion and strength. Crutches and a knee brace are used as needed, with gradual weight-bearing based on recovery progress. Physical therapy starts with gentle exercises, progressing to strengthening, balance training, and stationary cycling.
Return to Activity and Long-Term Monitoring: Sport-specific exercises are introduced as stability improves, with running typically starting around 3–4 months and more complex movements later. A full return to sports requires passing functional tests. Follow-up appointments track knee function, with some patients continuing maintenance exercises long-term.

Potential Risks and Complications

ACL reconstruction is generally successful but carries some risks. Infection, though rare, may require antibiotics or further surgery. Blood clots can form, potentially leading to pulmonary complications if untreated. Graft failure can occur due to technical issues, inadequate rehabilitation, or trauma. Some patients may experience lingering instability, stiffness, or numbness around the incision sites. Persistent pain, particularly at graft harvest sites, may also occur. In some cases, excessive scar tissue (arthrofibrosis) limits motion and requires further treatment. Hardware-related issues, such as screw irritation or migration, may occasionally need correction.

Dr Chong Xue Ling

Senior Consultant Orthopaedic Surgeon

Dr Chong Xue Ling is a Swiss fellowship-trained orthopaedic surgeon specialising in foot and ankle, as well as shoulder and elbow surgery.

She is a member of the European Group for the Study and Research of Minimally Invasive Surgery of the Foot and Ankle. For shoulder and elbow surgery, she completed her fellowship at La Tour Hospital, an accredited Swiss Olympic Medical Centre and learnt innovative techniques in arthroplasty for earlier return to activity as well as the stabilising techniques, developed to have greater strength without extensive fixation.

MBBS (S’pore)
MRCS (Ireland)
MMed Orthopaedic (S’pore)
FRCS Orthopaedic (Edinburgh)

Through active involvement in research, she aims to constantly improve existing treatment in the pursuit of quality care for her patients.

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ACL Surgery

Frequently Asked
Questions

Does ACL reconstruction prevent arthritis?

ACL surgery restores knee stability but does not fully prevent arthritis, especially if there was pre-existing cartilage damage. While reconstruction helps protect the joint by reducing instability-related wear, long-term knee care, including strength training and activity modifications, can help minimise the risk of arthritis over time.

Can the ACL graft stretch or loosen over time?

Some degree of graft laxity can develop as it matures and integrates with the body. However, a well-positioned graft, proper rehabilitation, and avoiding premature return to high-impact activities help maintain long-term stability and function. Overloading the knee too soon can compromise graft integrity.

How long will I need to wear a knee brace?

The duration of brace use varies based on the surgical technique, graft choice, and individual recovery. Some patients need a brace for 4–6 weeks to protect the graft and support early mobility, while others may discontinue it earlier if stability and muscle control are sufficient. The surgeon will provide specific guidance based on progress.

ACL Surgery

Indications for ACL Surgery