Anterior Cruciate Ligament (ACL) Reconstruction
What Is ACL Reconstruction and When Is It Used?
Anterior cruciate ligament reconstruction is an operation that replaces a torn ACL with a tendon graft. The ACL lies in the centre of the knee and helps control forward movement and rotation of the tibia beneath the femur. Reconstruction aims to restore functional stability when an ACL-deficient knee cannot meet a person's work, sport or everyday movement demands.
Reconstruction is different from simply stitching the torn ends together. The graft is passed through bone tunnels and fixed where the native ligament attached so that it can incorporate and remodel over time. It is not an automatic treatment for every ACL tear; the ACL tear guide explains injury patterns, diagnosis and non-surgical care in more detail.
Who Is a Candidate and Who May Not Need Surgery?
Surgical assessment is appropriate when the knee repeatedly gives way despite rehabilitation, when a person plans to return to pivoting or contact sport, or when an occupation requires dependable rotational stability. A repairable meniscus tear or another ligament injury may also affect the recommendation. The decision combines symptoms, examination, imaging, activity goals and the person's ability to complete a long rehabilitation programme.
A stable partial tear, a lower-demand lifestyle or good function after structured rehabilitation may support non-surgical management. Age alone neither requires nor rules out reconstruction. Surgery may be postponed when the knee remains swollen and stiff, while active infection, uncontrolled medical problems or inability to participate in rehabilitation must be addressed before an elective procedure.
Preparing for ACL Reconstruction
Preparation starts by confirming the diagnosis and reviewing the menisci, cartilage and other ligaments. X-rays help assess bone and alignment, while MRI defines soft-tissue injury. If swelling is pronounced or the knee cannot fully straighten, pre-operative rehabilitation is used to restore motion, improve quadriceps control and normalise walking before surgery.
Tell the surgical and anaesthetic teams about all medicines, blood thinners, allergies, previous clots and anaesthetic problems. Smoking and nicotine can impair healing, so stopping is encouraged. Follow the team's individual fasting and medication instructions, arrange transport home and prepare a safe space for rest, cold application and movement with crutches.
- Discuss whether associated meniscus or cartilage treatment could change weight-bearing restrictions.
- Plan time away from work according to sitting, walking, stair and lifting demands.
- Practise prescribed early exercises and safe crutch use before the operation.
How Is ACL Reconstruction Performed?
ACL reconstruction is usually performed with knee arthroscopy. A camera enters through a small portal so the surgeon can inspect the joint, confirm the ACL tear and evaluate the menisci and cartilage. Separate small incisions allow instruments to treat associated injuries and prepare the graft.
Tunnels are created in the tibia and femur at the planned attachment sites. The graft is drawn through the tunnels, tensioned and secured with fixation devices while the knee's motion and stability are checked. Tunnel position, graft tension and secure fixation are important because the new ligament must guide movement without becoming too loose or restricting the knee.
A meniscus repair may be completed during the same arthroscopy when a suitable tear is found. This helps preserve meniscal tissue but can require slower progression of bending and weight bearing than an isolated ACL reconstruction.
ACL Graft Options
An autograft uses the patient's own tissue. Common choices are the hamstring tendons, the central patellar tendon with small bone blocks, and the quadriceps tendon. Each has trade-offs involving incision location, kneeling discomfort, anterior knee pain, temporary muscle weakness, graft size and the demands of the intended sport or occupation.
An allograft comes from screened donor tissue and avoids harvesting a tendon from the patient. It may be considered in selected circumstances, including some revision or multiple-ligament operations, but graft choice also considers age, activity and incorporation. There is no single best graft for everyone; the decision should explain the advantages, limitations and rehabilitation implications of each suitable option.
Anaesthesia and Procedure Time
The operation may be performed under general anaesthesia or regional anaesthesia that numbs the lower limb, sometimes with sedation. The anaesthetist selects an approach according to health, preferences and the planned procedure. Local anaesthetic and a combination of pain medicines may be used to support early comfort and movement.
Procedure time varies with graft preparation, anatomy and additional meniscus, cartilage or ligament work. Many isolated reconstructions are managed as day surgery, but medical needs or a combined operation may require longer observation. Discharge depends on stable vital signs, controlled symptoms and safe movement rather than a fixed number of hours.
The First Days After ACL Surgery
Early priorities are controlling pain and swelling, regaining full knee extension, activating the quadriceps and walking safely. Keep the dressing dry as instructed, use a wrapped cold pack rather than placing ice directly on skin, and elevate the leg while resting. Prescribed pain medicine should be taken only at the stated dose and duration.
Crutches are commonly used at first and weight bearing often progresses as comfort and control allow after an isolated reconstruction. A brace is not identical for every patient. Meniscus repair, cartilage treatment or another ligament procedure can require specific limits, so another person's protocol should not be copied.
- Perform ankle pumps and permitted knee-motion exercises to support circulation and mobility.
- Monitor the wound, temperature, calf symptoms and circulation in the foot.
- Use the planned follow-up and physiotherapy schedule to guide each progression.
ACL Reconstruction Rehabilitation Timeline
Rehabilitation protects the healing graft while restoring motion, strength and neuromuscular control. Progress depends on clinical milestones and the knee's response, not the calendar alone. Increasing swelling, loss of movement or pain that remains worse the next day indicates that loading may need adjustment.
- Early protection: reduce swelling, regain extension, activate the quadriceps and establish a safe walking pattern.
- Movement and strength: restore flexion, develop lower-limb strength and progress from supported to controlled single-leg tasks.
- Running preparation: build strength symmetry, landing control and tolerance for repeated loading before beginning a graded running plan.
- Sport preparation: add jumping, deceleration, agility and change-of-direction drills with increasing complexity.
- Return to participation: combine objective testing, sport-specific practice, confidence and workload progression.
Returning to Work, Driving and Sport
A desk-based role can usually be resumed before work involving prolonged standing, ladders, kneeling, carrying or unpredictable turning. The plan considers swelling, safe walking, transport and the ability to take breaks. Driving should wait until the person is no longer limited by a brace or sedating medicine and can perform an emergency stop safely.
Return to pivoting sport commonly takes nine months or longer, but time is only one part of the decision. Full movement, minimal reactive swelling, appropriate strength, controlled landing and cutting mechanics, sport-specific conditioning and psychological readiness are considered together. Training exposure should increase gradually before unrestricted competition.
Risks and Possible Complications
ACL reconstruction is established surgery but cannot guarantee a return to a previous activity level. General risks include infection, bleeding, a blood clot, anaesthetic problems and injury to nearby nerves or blood vessels. Knee-specific problems include stiffness, loss of extension, persistent pain or swelling, fixation problems and graft failure after inadequate incorporation or a new injury.
Graft harvest can also cause local symptoms. Patellar tendon grafts may be associated with anterior knee or kneeling discomfort, while hamstring or quadriceps harvest may produce temporary weakness in the relevant muscle group. Rehabilitation addresses these deficits, but symptoms and recovery differ between individuals.
Factors That Influence Results and Alternatives to Surgery
Outcome is influenced by graft choice and placement, associated meniscus or cartilage damage, restoration of motion, strength and movement control, smoking, rehabilitation adherence and exposure to another injury. A knee cartilage injury or combined ligament damage may change expectations and the recovery plan.
The main alternative is structured non-surgical rehabilitation with activity modification and, in selected cases, a functional brace. It may provide sufficient stability for people who avoid pivoting demands. Injections do not restore the mechanical function of a deficient ACL; recurrent giving way after an adequate programme warrants reassessment rather than repeated symptom treatment.
When Should You Contact a Doctor?
After surgery, contact the clinical team for increasing wound redness or drainage, fever, pain that is not controlled as expected, new calf swelling or a sudden loss of knee movement. Chest pain or shortness of breath requires urgent medical help. A cold or pale foot, or new numbness and weakness, also needs urgent assessment.
For an overview of related conditions and procedures, visit the Knee page. To discuss whether reconstruction fits your stability and activity goals, use the Contact page to request an individual assessment.