The operation is performed arthroscopically (keyhole). A graft is harvested — commonly the hamstring tendons from the inner side of the knee, or the middle third of the patellar tendon. The graft is prepared and passed through tunnels drilled in the thighbone and shinbone, positioned where the original ACL was. It is secured with screws, buttons, or other fixation devices. If there is a meniscal tear, this is repaired or trimmed at the same time. The operation takes one to one and a half hours.
ACL reconstruction is recommended for patients with a torn ACL who experience recurrent knee instability or giving way, particularly those who wish to return to pivoting sports or have physically demanding occupations. Not everyone with an ACL tear needs surgery — the decision depends on activity level, symptoms, and the presence of associated injuries.
Intensive physiotherapy to strengthen the muscles around the knee and improve balance. Activity modification — avoiding pivoting and cutting sports. Bracing for certain activities. Many patients, particularly those with lower activity demands, manage well without surgery.
Pre-operative physiotherapy (prehabilitation) is strongly recommended. Evidence shows that patients who optimise their knee movement and muscle strength before surgery have better outcomes. Standard pre-assessment is required. You should stop smoking if possible.
Approximately 85–90% of patients achieve a stable knee that allows return to sport and demanding activities. The new ligament aims to restore directional stability and protect the knee from further damage. However, the knee may not be exactly as it was before the injury.
Knee swellingExpected
Expected after surgery and may persist for several weeks.
Graft site painCommon
Pain at the hamstring or patellar tendon donor site. Usually settles over weeks to months.
StiffnessCommon
Some loss of range of motion is common initially. Early physiotherapy is essential.
NumbnessCommon
An area of numbness on the outer aspect of the lower leg is common and usually resolves.
Graft failureUncommon
The new ligament may stretch or re-rupture. Risk is approximately 5–10%, higher in younger patients returning to pivoting sports.
Blood clotsUncommon
DVT despite preventive measures.
InfectionRare
Joint infection in approximately 0.5–1% of cases.
Nerve or vessel injuryRare
Rare damage to structures around the knee.
Ongoing instabilityUncommon
A small proportion of patients continue to experience some instability despite reconstruction.
Stiffness requiring MUARare
Arthrofibrosis — excessive scarring leading to loss of movement.
Usually performed under general anaesthesia. A nerve block may be used for post-operative pain relief. Spinal anaesthesia is an alternative.
Crutches are used for two to four weeks. Physiotherapy begins immediately and is essential for a good outcome. Jogging typically resumes at three months. Return to competitive sport is usually at nine to twelve months, guided by functional testing rather than time alone. Evidence shows waiting until at least nine months reduces the risk of re-injury by up to 84%. Full rehabilitation takes nine to twelve months.
Wound check at two weeks. Surgeon review at six weeks, three months, six months, and one year. Physiotherapy is the cornerstone of recovery and continues for many months.
When can I return to sport?
Return to competitive and pivoting sport is typically at nine to twelve months. Research shows that waiting until at least nine months and meeting performance criteria significantly reduces re-injury risk.
Which graft is best?
Both hamstring and patellar tendon grafts have excellent track records. Your surgeon will recommend the most suitable option based on your circumstances.
Will I get arthritis?
An ACL injury increases the long-term risk of knee arthritis regardless of whether surgery is performed. Reconstruction aims to stabilise the knee and reduce further damage.
Can the ACL be reconstructed again if it fails?
Yes, revision ACL reconstruction is possible but more complex, with slightly less predictable results.