Pain After A Pop In The Knee

An ACL tear typically occurs during sudden pivoting, awkward landings, or stops, which are common in sports such as basketball, soccer, and skiing. It usually starts with a moment, an awkward pivot during a pickup basketball game, a sudden stop on the soccer field, or landing just slightly wrong after a jump. You might feel a sharp pain, instability, or hear that telltale pop. You go down, maybe hoping it’s nothing, but your knee swells, and walking becomes difficult. That’s the moment many athletes, professional, weekend warriors, or even teenagers, begin their journey with an ACL tear.

Understanding how to recognize a minor knee issue needing minimal home treatment versus what may be an ACL tear can be critical to the proper treatment and the fastest path to healing.

What Is the ACL and Why Does It Matter?

Your knee is one of the most complex joints in your body, and the ACL is one of its most important components. It plays a huge role in keeping your knee stable and allowing you to move with confidence, whether you're sprinting down a field or simply walking downstairs.

The ACL (anterior cruciate ligament) is one of the four major ligaments in your knee, connecting your thigh bone (femur) to your shinbone (tibia). Its job is to stabilize the knee, especially during rotation, pivoting, and rapid direction changes. That makes it crucial for athletes, but also important for anyone who walks, runs, or climbs stairs.

When the ACL tears, it doesn’t heal on its own. And unlike muscles, ligaments don’t regenerate well without surgical reconstruction.

ACL Tear Symptoms: What You Might Experience

If you’ve injured your knee and are wondering if it’s your ACL, you’re not alone. Knowing what symptoms to look for can help you decide whether it’s time to see a doctor or get imaging.

Here’s what people often report:

• A “popping” sound or sensation at the moment of injury
• Immediate pain, sometimes severe enough to stop activity
• Swelling that begins within a few hours
• Instability or “buckling”, especially when trying to pivot or walk
• Loss of full range of motion

Some people can walk after an ACL tear, especially once swelling subsides, but the knee often feels unstable. Grade 1 (mild) tears may feel like soreness and instability under stress, but they’re rare. By two weeks post-injury, swelling may reduce, but instability often persists.

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ACL vs. MCL: Not All Knee Injuries Are the Same

Knee injuries can be confusing because symptoms often overlap. The ACL and MCL are two different ligaments with different functions, injury mechanisms, and treatment approaches. Understanding the difference is critical for proper recovery.

Many people confuse ACL and MCL (medial collateral ligament) injuries. Here’s how an ACL tear and MCL tear differ:

	ACL Tear	MCL Tear
Location	Inside the knee, central	Inside of the knee (medial side)
Mechanism	Pivoting, cutting, or landing	Direct blow to outer knee or overstretching
Sound	Often a pop	Less commonly a pop
Swelling	Fast and significant	Less severe swelling
Instability	Knee feels unstable or “gives out”	Usually more stiff than unstable
Healing Potential	Does not heal on its own	Often heals without surgery
First-line Treatment	Physical therapy or surgical reconstruction	Bracing, rest, and physical therapy
Surgery Needed?	Often required in active patients	Rarely required (unless Grade 3 + other injuries)
Return to Sport	6–12 months (after reconstruction)	4–12 weeks (depending on severity)

Key difference: An MCL tear can often heal with rest and bracing. An ACL tear usually won’t.

Can You Tear Both ACL and MCL at Once?

Yes, and this is more common than people think, especially in sports injuries. This is called a combined ligament injury and often involves the ACL, MCL, and/or meniscus. These cases require specialized surgical planning and longer rehabilitation timelines, making early diagnosis even more critical.

How to Know Which One You’ve Injured

While some clues (pain location, swelling speed, mechanism) may point toward one ligament over the other, you cannot reliably self-diagnose an ACL or MCL tear. Some people with a complete ACL tear are still able to walk or bend their knee, which can be misleading.

We recommend consulting one of our sports medicine specialists or an orthopedic knee surgeon as soon as possible. A timely and accurate diagnosis gives you the best chance of a full recovery and of avoiding chronic knee issues.

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Adolescent ACL Tear vs. Adult ACL Tear

When it comes to ACL injuries, age matters. Kids and teens are still growing, and that can make treatment more complicated. What’s best for a 14-year-old soccer player may be very different from what’s recommended for a 30-year-old runner.

ACL injuries are increasing in adolescents, especially teenage athletes. The growth plates (areas of developing cartilage near the ends of long bones) in kids add complexity:

• Non-surgical approaches may be prioritized in younger teens to avoid damaging growth plates.
• Modified surgical techniques (like physeal-sparing procedures) are used if surgery is necessary.
• Rehabilitation may need to be longer to protect future growth and return-to-play safely.

In adults, decisions are often based on lifestyle, activity level, and degree of instability.

ACL Tear Treatment Options

Surgery isn't always required for an ACL tear, but it can often be recommended. Once you’ve torn your ACL, the big question is: Do you need surgery? The answer depends on your goals, age, activity level, and the nature of the tear. For some, physical therapy may be enough. For others, reconstruction is the most straightforward path back to full function. Your treatment path is specific to you, and our specialists will build a plan that meets the needs of your injury and desired recovery outcome.

What Not To Do After an ACL Tear

Sometimes what you don’t do is just as important as what you do. The wrong move after an ACL tear can worsen the injury or lead to complications down the line.

• Don’t ignore instability. Repeated “giving out” episodes can damage the meniscus or cartilage.
• Don’t rush rehab. Returning to play too soon raises your risk of re-tear (or injuring the other knee).
• Don’t skip the MRI. X-rays won’t show ligament damage. An MRI is needed to confirm the tear and check for other injuries.
• Don’t rely solely on a knee brace if you're planning to return to sport, it doesn't replace ligament function.

Leaving an ACL tear untreated can lead to further joint damage, including cartilage wear or meniscus tears.

Can You Still Use Your Knee with a Torn ACL?

Some people can still walk, squat, or bend their knee shortly after tearing their ACL. However, without stability, these motions can cause further injury. If you suspect you have an ACL tear we recommend you see a orthopaedic specialist as soon as possible for a comprehensive evaluation.

Life After an ACL Tear: Hope, Patience, and Progress

An ACL tear is a detour, not a dead end. With the right care, commitment, and patience, people of all ages get back to running, jumping, and playing, often even better than before.

Tearing your ACL can feel like the end of your athletic identity, but it’s not. Thousands of people, from high school athletes to weekend hikers to pro players, successfully return to sports and active lifestyles every year.

The key is getting the right diagnosis, choosing the right treatment path for your goals, and committing to smart, structured rehab.

Diagnosis: Why You Need a POA Orthopaedic or Sports Medicine Specialist

While some symptoms can help differentiate between the two, it’s extremely difficult to diagnose knee ligament injuries accurately without imaging and specialist assessment.

Here’s why seeing a POA or orthopedic knee specialist is essential:

• Physical tests (like Lachman or valgus stress test) must be performed with skill and interpreted in context.
• MRI scans are required to confirm the exact ligament involved and assess associated injuries (meniscus, cartilage).
• Misdiagnosis can delay proper healing. For example, treating an ACL tear like an MCL sprain could lead to long-term instability or joint damage.

Bottom Line: Always get a clinical evaluation with a knee specialist, especially if you heard a pop, felt instability, or have swelling. Don’t self-diagnose based on symptoms alone.

Can You Recover from an ACL Tear? Here’s What to Expect

Tearing your ACL may feel overwhelming, but it's not the end of your active lifestyle. Whether you're a competitive athlete or someone who just wants to move without fear, recovery is possible with the right approach. From early diagnosis and personalized treatment plans to structured rehab and return-to-play timelines, every step forward matters. Understanding your options is the first step toward getting back to what you love, with strength and confidence.

If you’re reading this, you may be worried about what’s next. Take a breath, you’re not alone. Understanding your injury is the first step toward healing. Now it’s time to take action. If you suspect an ACL tear, don’t wait. Get evaluated by a sports medicine physician or orthopedic specialist. Early diagnosis means earlier healing and a better chance of getting back to doing what you love.

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ACL Tear vs. Meniscus Injury: Key Differences at a Glance

While both ACL and meniscus injuries are common in athletes and active individuals, they are very different in structure, symptoms, and recovery needs. Knowing the distinctions can help guide proper diagnosis and treatment.

How an ACL Tear and Meniscus Tear Happen

• ACL Tear:
  • Typically from a sudden pivot, change in direction, or awkward landing
  • Often non-contact, though can also result from trauma
  • Common in sports like soccer, basketball, skiing
• Meniscus Tear:
  • Often caused by twisting the knee while the foot is planted
  • Can occur with or without an ACL tear
  • May result from degeneration in older adults or a sharp movement in younger athletes
    

Primary (Immediate) Symptoms

Symptom	ACL Tear	Meniscus Tear
Popping Sound	Very common	May occur, but less dramatic
Swelling	Rapid (within hours)	Gradual (over 24–48 hours)
Instability	Knee may "give out"	Usually feels stable
Pain Location	Deep or central knee	Side or back of knee (depending on tear location)
Mobility	Loss of motion due to swelling and instability	May still walk, but discomfort with twisting/squatting

Prolonged/Chronic Symptoms (If Left Untreated)

Symptom	ACL Tear	Meniscus Tear
Knee Giving Out	Frequent instability, especially during pivoting	Rarely unstable
Locking or Catching	Uncommon	Very common — knee may catch or lock during motion
Grinding or Clicking	Occasionally	Common, especially with movement
Degeneration Risk	Higher if combined with meniscus injury	Increases risk of arthritis over time
Return to Activity	Difficult without surgery for active individuals	Sometimes possible without surgery, depending on severity and tear location

A meniscus tear often presents with joint line tenderness and mechanical symptoms (like locking), while an ACL tear leads to feelings of instability and swelling shortly after injury. However, since both can coexist, and symptoms can overlap, accurate diagnosis with an MRI and specialist evaluation (by a POA or orthopedic physician) is essential. Read more about meniscus tears.

Quick Overview

	ACL	Meniscus
Function	Stabilizes the knee	Cushions and supports joint movement
Injury Type	Ligament	Cartilage
Instability?	Yes	Rarely
Locking	Rare	Common
Needs Surgery	Often (for active patients)	Sometimes, depending on tear type

This blog post is meant to be informative and should not act as a self-diagnosis tool. If you’d like to see one of our doctors, please contact us here.