Back to the Gym After an ACL Injury

What is an ACL injury?

An ACL injury is a sprain or tear of the anterior cruciate ligament, a band that runs through the middle of the knee. The American Academy of Orthopaedic Surgeons says it stops the shinbone sliding out in front of the thighbone and gives the knee rotational stability. Singapore General Hospital calls it one of the most common knee injuries.

1. 01How it happensMost tears involve no contact. Changing direction fast, stopping suddenly, slowing down while running or landing a jump badly (AAOS).
2. 02What it feels likeA pop, the knee giving way, then pain and swelling within 24 hours (AAOS, SGH).
3. 03Who is most at riskPeople in high-demand sports such as football and basketball (SGH).

Does a torn ACL need surgery?

Not always. SGH says a torn ACL will not heal without surgery, but non-surgical care can work when the knee is otherwise stable, mainly for older or less active people. The NHS says not all ACL injuries need surgery, and AAOS calls non-surgical care always an option. Your surgeon decides with you.

Either way, the leg has to get strong again. How a broader knee injury plan works, meniscus included, is on our knee injury training page. This page stays with the ACL and the late stage.

What are the rehab phases after ACL surgery?

Four phases, each passed by milestones rather than dates. SGH describes the same order: restore movement, strengthen while protecting the new ligament, then a functional return to activity. SGH also has patients wear a brace for the first six weeks. The time ranges below are from Physio & Sole, a Singapore physiotherapy clinic.

How long until you can return to sport after an ACL tear?

Usually 9 to 12 months after reconstruction. Physio & Sole puts ACL recovery at 9 to 12 months depending on your sport, with running often back at 3 to 6 months once criteria are met. The NHS says sport can take up to a year, and most people return to work after about 4 to 6 weeks, depending on the job.

Why not sooner? A 2021 commentary in the International Journal of Sports Physical Therapy cites a seven-fold greater risk of injury for people who returned to sport before nine months after surgery. The calendar is a floor, not a pass.

When can you start strength training at the gym after ACL surgery?

When your surgeon or physio says so, usually during the strength phase. They know the graft, the knee and what the early weeks showed. A coach does not set that date and does not shorten it.

What tests does a physio use before return to sport?

Your physio compares the injured leg with the healthy one and expresses it as a percentage, the limb symmetry index. If the injured leg hops 90cm and the other hops 100cm, that is 90%. The IJSPT commentary sets out how these tests are used:

The same authors warn that a symmetrical score does not prove good movement. Someone can hit perfect symmetry and still be underprepared, which is why physios also watch how you land and change direction.

What does a personal trainer do in late-stage ACL rehab?

A coach builds the strength and control the physio's tests look for, inside the physio's plan. The physio assesses, treats and decides when you return. The coach adds coached sessions between physio visits, where most of the strength comes back.

1. 01Single-leg strengthSplit squats, step-ups, single-leg press and hinge work, loaded a little more each week, with the injured leg leading so it closes the gap on the other.
2. 02Landing mechanicsSoft, quiet landings with the knee tracking over the toes, first on two feet, then one, only once your physio clears jumping.
3. 03Progressive loadingOne change at a time: more weight, more reps or a harder variation. A session that leaves swelling the next day means the next one steps back.
4. 04ConditioningBike, upper body and trunk work so overall fitness keeps pace while running is still limited.
5. 05Practice for the testRehearsing the movements your physio will test, so test day measures the knee and not nerves.

Athletes heading back to a sport often move from here to a strength and conditioning coach. If the knee kept you out of training for months, the pacing in returning to exercise after a long break applies too.

When should you stop training and see your doctor?

Stop the session and contact your surgeon or physio if the knee gives way, swells during or after training, or the pain is sharp. AAOS notes that going back to activity on an unstable knee can worsen instability and damage other parts of the knee. The NHS lists signs after recent ACL surgery that need urgent help:

1. 01Infection signsA high temperature, feeling hot and cold, or pus from the wound.
2. 02A knee getting worseTenderness, swelling, pain or redness that is not improving.
3. 03Clot signsThrobbing or cramping pain in the leg.

Emergency: leg pain and swelling with difficulty breathing or chest pain. In Singapore, call 995.

How do your coach and physio share the plan?

You carry the plan between them. The physio stays in charge, and the coach reports back through you.

Before the first session, send the coach your physio's notes, cleared exercises, limits and the date of surgery.

Do you need a physio or a personal trainer for ACL rehab?

Both, in that order. The physio leads the whole recovery and the return-to-sport decision. A coach adds coached volume once you are cleared.

Who to see first is set out in physio or personal trainer.

How do you start with a Fit Titans coach after an ACL injury?

Message us with your surgery date, your physio's notes and your goal. A coach comes to your home, your condo gym, a park or a gym that allows outside trainers. The first session is a paid trial at 10% off the coach's rate. After it, sessions come in packs from 5, paid by PayNow. How coaching fits with physio is on our injury rehab page.