ACL Reconstruction

The knee is where the femur, tibia, and kneecap meet, held together by four main ligaments. The anterior cruciate ligament runs diagonally through the center of the joint, from the back of the femoral notch to the front of the tibia.

Its job is rotational control: it stops the tibia sliding forward and limits twisting when you decelerate, land, or change direction. The menisci, the shock-absorbing wedges often torn alongside it, matter just as much. A torn ACL sits in joint fluid with a poor blood supply, which is why it does not reliably heal.

A torn ACL is generally not stitched back together. It is reconstructed: a new ligament is built from tendon tissue and placed along the path of the original.

The operation is arthroscopic, with a slightly larger incision to harvest the graft. Tunnels are drilled at the exact footprints where the native ligament attached, and the graft is pulled through and fixed at both ends. Your body then remodels that tendon into something that behaves like a ligament, which is why recovery takes months rather than weeks.

Most ACL tears involve no contact with another player. They happen when the foot is planted and the knee twists inward under a decelerating body.

• Cutting, pivoting, and deceleration in soccer, lacrosse, basketball, and football
• Landing from a jump with the knee collapsing inward
• Skiing, where a fall drives the knee into rotation while the boot holds the leg
• Direct blows to the outside of the knee

Young female athletes in cutting sports have a higher rate of ACL injury than their male counterparts, one reason neuromuscular training programs are worth doing before an injury happens.

• A pop felt or heard at the moment of injury
• Swelling within the first few hours, not the next day
• Inability to keep playing
• A knee that shifts, buckles, or gives way on turns and stairs

A knee that locks or will not straighten often means a displaced meniscus tear alongside the ACL, which changes how quickly surgery should happen.

A torn ACL can usually be diagnosed in the office. The Lachman test is the most reliable examination finding, and the pivot shift reproduces the rotational instability patients feel.

X-rays rule out fracture, particularly in adolescents with open growth plates. MRI confirms the tear and shows what else was injured: the menisci, cartilage, and collateral ligaments. That picture drives the plan, because a repairable meniscus tear changes both the timing and the details of surgery.

Not every ACL tear needs an immediate operation, and it is worth saying so plainly. Some people with lower physical demands who do not pivot for work or sport do well with rehabilitation alone.

Reconstruction is recommended when you want to return to cutting or pivoting sport, when the knee gives way in daily life, or when there is a meniscus tear worth repairing. Repeated giving-way episodes damage the menisci and cartilage, and that damage is not reversible. Timing matters too: operating on a swollen, stiff knee raises the risk of scar tissue, so most patients first spend two to four weeks restoring extension and quadriceps control. Skeletally immature athletes need techniques that protect open growth plates.

• Do the prehabilitation. A knee that straightens fully and can fire the quadriceps is the strongest thing you control.
• Stop nicotine; it impairs graft incorporation and wound healing.
• Hold anti-inflammatories and blood thinners as directed.
• Have crutches, a brace, and ice ready, and book therapy in advance.
• Arrange a driver and someone to stay the first night.

1. Anesthesia and examination. General anesthesia with a regional block, then an exam under anesthesia to grade instability.
2. Arthroscopy. The joint is inspected and meniscus and cartilage injuries addressed, repairing meniscus tissue whenever the tear allows.
3. Graft and tunnels. The graft is harvested and sized, and tunnels are drilled at the native footprints, which restores rotational control rather than just front-to-back stability.
4. Fixation. The graft is secured at both ends and the knee taken through a full range to confirm stability.

Choosing a Graft

There is no single right answer, and the trade-offs are real. This is decided together before surgery.

• Patellar tendon (bone-tendon-bone) autograft. Bone plugs heal into bone tunnels quickly, with a long track record in pivoting athletes. The trade-off is kneeling discomfort, which matters if you kneel for work or sport.
• Hamstring autograft. Smaller incision and much less kneeling pain. The trade-off is slower healing of soft tissue inside a bone tunnel and some weakness at deep flexion.
• Quadriceps tendon autograft. A strong, large graft with less kneeling pain than a patellar tendon graft. The trade-off is early quadriceps weakness.
• Allograft (donor tissue). No harvest site pain and a shorter operation, which suits older or lower-demand patients. In young athletes returning to pivoting sport, allografts fail substantially more often than a patient's own tissue, so they are rarely the first choice there.

For patients at higher risk of a second tear, including revisions, very loose joints, and young athletes returning to high-level pivoting, a lateral extra-articular augmentation may be added to protect the graft against rotation.

Weeks 0 to 2

Crutches and a brace, weight bearing as tolerated for an isolated reconstruction; most people are off crutches within one to two weeks. Priorities are full extension, quadriceps activation, and swelling control. A repaired meniscus means restricted weight bearing.

Weeks 2 to 6

Motion progresses toward full, gait is normalized, and cycling begins.

Weeks 6 to 12

Progressive strengthening and single-leg control. Quadriceps strength is the limiting factor, and it is measured rather than guessed.

Months 3 to 5

A graded running program once quadriceps strength and mechanics are adequate, then jumping and landing work.

Months 5 to 9

Cutting, pivoting, and sport-specific drills, then non-contact team training.

Months 9 to 12

Return to pivoting sport is decided by testing, not the calendar: strength close to the other leg, hop tests, sound landing mechanics, and honest psychological readiness. Returning before nine months is associated with a higher chance of a second ACL injury.

Possible complications include infection, blood clot, bleeding into the joint, and a patch of numbness beside the incision from a small skin nerve, which is common and usually fades. Stiffness or loss of extension can occur, and is the main reason surgery is delayed until the knee calms down.

The graft can stretch or retear, particularly with an early return to sport, and the opposite knee is also at risk. Other issues include lingering quadriceps weakness, kneeling discomfort, harvest site pain, growth disturbance in skeletally immature patients, and long-term joint wear, which is higher when meniscus tissue has been lost. No surgeon can guarantee an outcome.