Torn your ACL?

A SURGEON’S PERSPECTIVE

A few things you should know up front:

• Not every ACL tear needs surgery.

• The graft choice matters. It should be tailored to your knee, your sport, and your goals.

• Rehab is half the operation. The best surgery in the world fails without good physio and good rehab.

Stage 1 — I think I’ve torn my ACL. What now?

ACL injuries usually happen during a pivot, a sudden change of direction, or a bad landing. You often hear or feel a “pop”, the knee swells within hours, and it feels unstable or like it wants to give way.

What to do in the first 48 hours:

• Ice, elevate, and rest. Use a brace or strapping if you have one.
• See your GP or a physiotherapist within a few days.
• Get an MRI organised — your GP or physio should be able to facilitate this under the current ACC pathways.

You should be referred to a knee specialist if any of these are true:

• The MRI confirms an ACL tear.
• Your knee continues to give way during normal activities.
• You play a pivoting or contact sport and want to return to it.
• You have an associated meniscus tear or other ligament injury.

Stage 2 — Diagnosis and imaging

A torn ACL is diagnosed by combining three things:

• Your story. How it happened, what you felt, how the knee has behaved since.
• Examination. Our team will check stability with specific tests (Lachman, anterior drawer, pivot shift).
• MRI scan. Confirms the diagnosis, shows the tear pattern, and reveals any associated injuries — meniscus tears, cartilage damage, bone bruising, or other ligaments.

Why the tear pattern matters. Not all ACL tears are the same. Where the ligament has torn — at the femur, in the middle, or at the tibia — changes what we can do. In some cases, a repair of your own ACL is possible rather than a reconstruction (more on that in Stage 4).

Associated injuries. Roughly half of ACL tears come with a meniscus injury. Around 1 in 10 involves another ligament. These change the urgency of surgery and sometimes the approach. Our team will discuss your MRI findings in detail at your consultation.

Stage 3 — Do I actually need surgery?

This is often the most important discussion we have in clinic. An ACL tear does not automatically mean you need surgery. Many patients can function well with appropriate rehabilitation, while others remain at high risk of further instability.

The aim of our consultation is to assess your individual risk of recurrent knee instability (“giving way”) based on factors such as your sporting demands, occupation, associated injuries, knee laxity, and goals for the future.

Each instability episode can cause additional and irreversible damage to the cartilage and meniscus within the knee. The primary role of ACL surgery is therefore not simply to reconstruct the ligament, but to restore stability and help protect the knee from further damage over time.

You can live well without an ACL for straight-line activities:

• Walking, hiking, running on even ground
• Cycling
• Swimming
• Many gym-based activities

Some people return to social or recreational sport without an ACL, provided:

• Their leg muscles are strong and well-conditioned
• The knee is not giving way
• There are no other knee injuries (meniscus, other ligaments) that need surgical treatment

ACL repair or reconstruction is recommended if:

• You want to return to a pivoting or high-impact sport (rugby, league, netball, football, basketball, skiing, snowboarding)
• Your job or lifestyle involves cutting, jumping or landing
• You have associated injuries — a repairable meniscus tear, another ligament tear — that need surgery anyway
• Your knee keeps giving way despite good rehab

Stage 4 — Choosing the right graft for you

The graft is the new ligament that replaces your torn ACL.

We individualise the choice based on your age, sport, body type, knee anatomy, occupation, and what matters most to you (kneeling, sprint speed, hamstring strength). The right answer for a 17-year-old netballer is different to the right answer for a 38-year-old recreational skier.

Here are the options we commonly use:

ACL Repair (not a graft — your own ACL)

Recent advances in surgical technique and our understanding of ACL healing have made repair of the torn ACL possible in specific cases.

• When it’s an option: certain tear patterns where the ACL has torn away from the femoral attachment.
• What it offers: a more “natural-feeling” knee, faster healing (around 5 months), earlier return to sport.
• Decision point: the ACL’s condition is assessed at the start of every surgery. If a repair is appropriate, it will be offered. If not, we proceed with reconstruction.

Hamstring tendon — single bundle

• Most common ACL graft worldwide.
• Uses two of your hamstring tendons.
• Failure rate: ~10%.
• Side effects: some hamstring weakness, cramps, mild ongoing strain; kneeling discomfort in ~10%.
• Best for: low- to medium-demand activities, knees at risk of stiffness, or where some native ACL is healing.

Hamstring tendon — double bundle

• Recreates the natural two-bundle anatomy of the ACL.
• Failure rate: ~5%.
• Side effects: as for single-bundle hamstring.
• Best for: medium- to high-demand knees, especially where kneeling discomfort would be a problem (tradies, gardeners, kneeling with young children).

Patellar tendon — bone-tendon-bone

• Uses the middle third of your patellar tendon with bone plugs at each end.
• Failure rate: ~5%.
• Side effects: kneeling discomfort in ~20%.
• Best for: high-demand knees, including professional and competitive athletes.

Quadriceps tendon

• Uses a strip of the quadriceps tendon above the kneecap.
• Failure rate: ~7%.
• Side effects: rehab is more demanding early on; potential for long-term quadriceps weakness.
• Best for: revision (repeat) ACL surgery, and selected primary cases.

ALL (anterolateral ligament) augmentation

• Performed alongside the ACL reconstruction in high-risk knees.
• Purpose: improves rotational stability, reduces graft failure risk.
• Side effects: can make the knee feel too tight or stiff.
• Best for: young patients, pivoting sports, generalised joint laxity, or revision cases.

The bottom line. Graft choice matters most in the first 12 months after surgery, when most graft failures occur. We’ll talk through your options at the consultation.

Stage 5 — Prehab

Arguably the second most important part of the ACL journey. Your knee function before surgery has a major influence on both your recovery after surgery and your overall outcome.

The goals during prehab are to:

• regain full knee extension (getting the knee completely straight)
• improve knee bending
• reduce swelling and inflammation
• restore a normal walking pattern
• build strength in the muscles around the knee, particularly the quadriceps and hamstrings
• comfortably tolerate time on a stationary bike

Working closely with your physiotherapist during this phase is essential. Going into surgery with a calm, mobile, and strong knee gives you the best platform for a smoother rehabilitation and successful return to sport and activity.

Stage 6 — Surgery day and the first two weeks

ACL reconstruction is done as a day-stay procedure under general anaesthetic, sometimes with a regional nerve block for pain control. Surgery takes around 45–90 minutes.

On the day:

• Arrive fasted as instructed.
• After surgery you’ll be in recovery for a couple of hours, then home the same day with crutches and a knee brace.

First two weeks:

• Pain is usually well-controlled within the first 3–4 days.
• Use of crutches, brace and weight-bearing status will be dictated by whether the meniscus or other ligaments were repaired during surgery.
• Swelling is normal and settles within about 4 weeks.
• A simple home exercise programme, provided by the hospital, starts on day one — gentle range of motion, quadriceps activation, swelling control.
• Your first physio appointment is usually within the first two weeks.

Stage 7 — Rehabilitation: 2 weeks to 6 months

Rehab is the most important part of this journey.

If you have had a reconstruction rather than a repair, the graft you receive is not a ligament — yet. Over the first 9 months it remodels into ligament tissue inside your knee. Pushing it too hard, too soon causes failure. Pushing it too gently delays your return. Good rehab is graded, structured, and outcome-driven.

Key principles:

• Consistent physio after surgery reduces stiffness and lowers the risk of graft failure.
• The graft itself takes around 9 months to mature.
• Full muscle strength can take up to 2 years to return.

We are fortunate to have an excellent group of physiotherapists in Taranaki with experience in ACL rehabilitation. We continue to improve our shared expertise through regular meetings and sharing ideas.

Stage 8 — Return to sport: months 6 to 12

This is the stage patients most want to skip — and the stage that decides whether your operation succeeded long-term.

Our rules are simple:

• No return to pivoting sport before 12 months for a full reconstruction.
• ACL repairs and partial reconstructions can return at 6 months.
• You must pass a formal Return to Sport (RTS) assessment with your physiotherapist before you play. This is considered mandatory in our practice.
• Even then, the data is honest:
  • About 70% of patients return to some form of sport by 2 years.
  • About 50% return to the same high level they played at before injury.
  • One of the biggest predictors of a second ACL tear is returning to sport too early or without passing RTS criteria.

What the RTS assessment looks at:

• Quadriceps strength (limb symmetry index ≥90% of the uninjured side)
• Hop tests (single, triple, crossover, side hop)
• Movement quality on landing and cutting
• Psychological readiness (ACL-RSI score)
• Sport-specific demands

If you don’t pass, you don’t play. We keep working until you do. That single rule is one of the most important things we can do to protect your knee long-term.

Further surgeries

A small number of ACL patients may require additional “fine-tuning” surgery during their recovery. This occurs in approximately 5–10% of patients, and may be higher in professional or pivoting athletes.

The most common reasons include:

• A further pivot injury during rehabilitation, resulting in cartilage or meniscus damage requiring arthroscopy or debridement.
• Knee stiffness or loss of range of motion in the first year after surgery, occasionally requiring a scar tissue release procedure.

These procedures are generally much smaller than the original ACL surgery. In most cases, there are no significant restrictions afterwards, and patients are encouraged to resume rehabilitation immediately.

Any decision regarding further surgery is made collaboratively between the patient, surgeon, physiotherapy team, and rehabilitation providers to ensure the best long-term outcome.