Swelling often occurs immediately after an ACL injury. In some cases, swelling may develop up to 24 hours later and may last up to a week.
A person who experiences an acute anterior cruciate ligament (ACL) tear of the knee is likely to report some combination of the following knee symptoms:
- Initial sharp pain. Unlike progressive knee conditions, such as knee osteoarthritis, symptoms of an ACL tear are sudden onset and can almost always be traced back to a specific incident or injury.
- Swelling after the injury. Swelling often occurs immediately after the injury. In some cases, swelling may develop up to 24 hours later. Swelling may last up to a week.
- Deep, aching pain in the knee. The pain may be worse when walking or climbing stairs.
- A feeling the knee is “giving out.” Instability may be especially noticeable during activities that strain the knee joint, such as walking downstairs and pivoting on one leg.
See Guide to Knee Joint Anatomy
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- Restricted range of motion. It may be particularly difficult to straighten the affected knee.
- The knee may feel warm to the touch. This is due to bleeding within the knee joint.
- Inability to bear weight. In Grade II or III injuries, the pain and swelling may be too severe to stand or walk without assistance or limping.
- Tenderness around the knee joint. This area may be painful to the touch.
- Bruising around the knee. Bruising can occur all around the knee area.
- Numbness. In some cases, such as a severe ACL tear, a person may lose feeling (numbness) down the leg, below the knee.
While some symptoms occur immediately after injuring the ACL, such as swelling and tenderness, others may appear or get worse in the days following the injury, such as bruising.
See Common Running Injuries: Knee Pain
Without treatment, the swelling and pain in the knee generally subside over a period of several weeks; however, knee instability may often persist. Instability can limit the person’s ability to participate in athletics and even do normal, daily activities. In particular, it may be difficult for the person to stand up from a seated position or go down stairs.
See The P.R.I.C.E. Protocol Principles
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Additional Symptoms
Other structures in the knee, such as the meniscus and medial collateral ligament (MCL), are often damaged with ACL injuries. These other injuries may cause additional symptoms, such as knee locking—the inability to bend or straighten the knee—to occur and may require additional treatment.
See Soft Tissue of the Knee Joint
Last updated: 16 August 2021
Google is good for a lot of things, but it can’t reach into our physical reality to diagnose and treat your knee injury. At least, not yet…
So, we asked a real doctor—orthopaedic surgeon Mr Benjamin Witte of Orthopaedics WA—all the things you ever wanted to know about anterior cruciate ligament (ACL) tears.
His main piece of advice is if you have a significant knee injury, especially if your knee swells, go see your GP and ask for an MRI scan. They can also provide on-the-spot pain relief. If you need further treatment, you’ll be referred to a specialist like Mr Witte.
But just in case you were genuinely curious, we also asked him to answer the 10 most common questions people Google about ACL tears. This is general information, not advice, and does not take into account your personal circumstances. As always, visit your health provider if you encounter an ACL issue.
1. What is an ACL injury?
Your ACL is a ligament that helps hold the two main bones of your leg—the tibia and femur—together. These are two of the biggest bones in the body.
An ACL injury is when the ligament tears slightly or separates entirely.
According to Mr Witte, “An ACL tear usually happens in a ball sport. It’s often a non-contact injury where the person has changed direction with a lot of momentum.
“For some reason—we don’t know why—the forces on the knee are too strong for the ACL and it tears (gives way or ruptures).”
If you tear your ACL, you’ll probably end up on the ground, rolling around in pain.
2. What are the symptoms of an ACL injury?
“You’ll experience a sharp pain when it happens, and within an hour or two your knee will swell up,” says Mr Witte.
“The swelling is caused because there is bleeding and blood will collect in the knee.”
But it gets better with time.
“Often what happens over the next few weeks is the knee will gradually settle down. The body will start to reabsorb the bleeding from the knee and the stiffness, soreness, limping and swelling will all start to settle down.”
While your knee might feel better, Mr Witte warns, “the ACL inside the knee is still ‘busted’”.
The main symptom long-term is having the knee give way when playing sport or when twisting and turning.
If you continue to strain your busted ACL, you might start doing secondary damage and injuring the cartilage, particularly if you play high-impact sports like basketball or football.
3. Can you walk with a torn ACL? How about driving?
“Surprisingly for some people, they can often get back to walking and they feel OK.”
Mr Witte explains that even with a torn ACL, you may find a few weeks after your injury that you can ride a bike and swim, go back to work, and do most normal things. Including driving.
But you will have problems with twisting and turning. Especially if you’re doing it quickly while running or playing sport.
4. Can it heal without surgery?
According to Mr Witte, “Only one or two per cent of the time does an ACL heal itself without surgery.
“It’s certainly not impossible but it is reasonably rare and for most people who bust their ACL, it doesn’t heal.”
Basically, if you bust your ACL, it’s unlikely it’ll heal on its own.
The knee will settle down and feel better after a few weeks, but the ACL is still busted.
5. When is surgery necessary?
“Most young, active, sporty people should probably have an ACL reconstruction," says Mr Witte.
“If you’re planning on going back to play sport in the future, you should have an ACL reconstruction.
“If you’re older and not planning on playing any sport that involves running, twisting and turning, your knee has settled down and you’re not really aware of the knee having a problem, then you may not need an operation.”
In terms of timing your surgery, Mr Witte says most specialists will advise you wait until your knee has settled down and is bending and straightening.
“We actually want to operate on a healthy, happy knee.”
6. How much will surgery cost?
It depends on a few things, the main one being whether you go through the public system or use your health insurance to go private.
Related: 3-step guide to accessing surgery in Australia
Mr Witte suggests that you should always ask your health fund to provide a quote of how much they’ll cover because surgery costs can vary depending on your surgeon and hospital.
7. Which graft is better for an ACL reconstruction?
In Mr Witte’s opinion, the hamstring graft is the best option.
“It doesn’t cause much pain or harm and you often won’t even realise it’s being taken,” he says.
Mr Witte uses hamstring grafts 90 per cent of the time. In his experience, they don’t seem to make the leg weak in the long-term, and provide a very strong, reliable graft.
“There are other grafts, which are OK,” he says.
“The patella tendon is strong, and the quads tendon can also be used and that’s reasonably good.”
Mr Witte doesn’t use the ligament augmentation reinforcement system (LARS) ligament.
“I tell my patients that it is basically a bit of plastic or polyester, it is likely to eventually fail, and they’ll end up with some plastic in their knee.”
8. How long will the knee hurt for after surgery?
The short answer is: your knee will be sore for a few days, but within 7-10 days it will usually be feeling pretty good.
Mr Witte puts a lot of local anaesthetic in the knee, so when his patient wakes up the knee is not that sore.
He adds that “the anaesthetist has already got some painkillers in your system [during surgery] and we always provide painkillers to take home”.
9. How long after surgery can you walk?
Mr Witte explains that this depends on your specialist.
“My rehab is fairly accelerated and aggressive rehab. So, I usually do the operation as a day case and I encourage the patients to walk on that same day.”
Mr Witte’s patients are advised their knee will be sore and they will be limping, but they’re allowed to walk on it and encouraged to get walking on it a day or two after surgery.
“Often when I see them at one week they’re already walking, often with a bit of a limp and sometimes the knee is still a bit stiff. But we try and get them walking from day one.”
10. How can you prevent ACL tears?
“I would certainly encourage people to keep playing sport,” Mr Witte says.
“If you’re playing one of the higher risk sports – footy, rugby, basketball, netball, soccer – then as well as normal training, you should go to the gym and work on general core strength and do lunges and squats.”
The last thing you knee-d to know
Mr Witte’s main piece of advice is if you have a significant knee injury, especially if your knee swells, go see your GP and ask for an MRI scan.
GPs can also provide on-the-spot pain relief. If you need further treatment, your doctor will refer you to a specialist.
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