In my practice as an orthopaedic surgeon, meniscus and ACL tears are among the most common knee injuries I treat. But they’re not always easy for patients to tell apart.
That’s because the symptoms are very similar. Both problems can cause pain and swelling, and make it harder for a person to move their knee normally. But they also have some important differences — including how likely they are to heal on their own.
That’s why it’s worth knowing what you’re dealing with. Let’s take a look at what sets these two knee injuries apart and what you should do if you’re hurt.
Recognizing a torn meniscus
What it is: The meniscus is a C-shaped piece of cartilage, or rubbery tissue. Located between the thigh bone and the shinbone, it acts as a cushion to absorb shock around your knee. Just like the name implies, a torn meniscus happens when it sustains a rip or tear.
How it happens: The meniscus can tear when a person’s knee makes a hard twist. This can happen suddenly, especially while playing a sport that involves fast twisting movements — like soccer, tennis, basketball, or football. Getting hit or tackled in the knee can also cause it to twist, leading to a meniscus tear.
But meniscus tears don’t just affect athletes. I’ve also seen many patients who have torn their meniscus through everyday movements, such as twisting awkwardly while getting up from a chair or stepping from one type of surface to another. Some people aren’t aware of any unusual movement before an injury. Older adults are especially likely to experience this type of tear, because aging causes the cartilage and meniscus in the knee to become thinner and weaker. So do conditions like arthritis.
What it feels like: A torn meniscus can cause pain (especially when twisting or squatting), stiffness and swelling. It might feel like your knee is locked straight (or close to it). You might also feel like your knee might give out if you put weight on it. Some people feel a pop when their meniscus tears but not always.
Often these symptoms don’t start right after the injury. Most people can still walk or even play sports on their injured knee at first. But over two or three days, the knee may gradually get stiffer and more swollen.
Recognizing an ACL injury
What it is: The anterior cruciate ligament (ACL) is a band of tissue that connects the thigh bone and shinbone. It keeps the knee stable when you’re pivoting or changing directions quickly. When the ACL is injured, it can stretch, partially tear, or tear completely.
How it happens: ACL injuries can occur when the knee is forced to bend or twist farther than normal. Activities in which someone suddenly slows down and quickly changes direction are a common culprit. Think downhill skiing, basketball, lacrosse, soccer, tennis, or gymnastics.
| Torn meniscus | ACL | |
| Pain | On the sides or back of the knee; may develop gradually | Deep inside the knee; typically immediately |
| Feeling a pop | Sometimes | Often |
| Swelling | Over 2-3 days | Immediately |
| Feeling like the knee is stiff or locked | Yes | No |
| Trouble bearing weight on the knee | Yes | Yes |
A direct blow to the knee can cause the ACL to tear, too. It often happens in football — but it’s not limited to sports. Falls and car accidents can also cause the ACL to tear.
What it feels like: “I felt a pop, then my knee just gave out.” That’s often how patients with ACL tears describe their injuries. Right away, a person will start to have pain (especially when they try to put weight on their knee), swelling, and a feeling of weakness in the knee. They might also have trouble bending their knees as much as they usually can.
Not sure what you have? Ask yourself this question.
If you’re having trouble figuring out whether you’ve injured your meniscus or your ACL, ask yourself this: Did I notice intense pain and swelling right away, or did it get worse over a few days?
Immediate symptoms often signal an ACL tear. Symptoms that come on slowly are often meniscus-related.
It’s also worth noting that the answer may be: both. A movement or fall that tears the ACL may also tear the meniscus.
While symptoms can offer important clues, there’s no substitute for a physical exam. So if you’re in doubt, give your doctor a call.
When to see a knee specialist
In some cases you may be able to manage a knee injury on your own. Many meniscus tears heal with simple rest and ice. But ACL tears sometimes require surgery — especially in athletes who want to return to a sport.
I recommend seeing an orthopaedic specialist if you:
- Have swelling or pain that isn’t getting better after a few days of rest, ice, and over-the-counter pain relievers
- Can’t fully bend or straighten your leg without knee pain
- Feel like your knee locks up or might give way underneath you
The specialists at Temple’s Orthopaedics and Sports Medicine Program are an excellent place to start. We have the expertise to diagnose knee injuries and help you recover quickly, so you can get back to doing what you love. Call 800-TEMPLE-MED (800-836-7536) to set up an appointment, or request one online.
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