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People often feel a loud pop in knee followed by pain sensation in their knees during movement. This is generally harmless and can affect any joint. However, people may also experience knee cracking and pain, which could be a sign of a ligament injury, meniscus tear, or patella tracking issues. Many people's knees creak or crack or even pop, a phenomenon known as crepitus. Most of the time it's not a big deal.

But a loud crack might give you pause—and rightfully so. This type of rupture can be accompanied by pain and swelling, which are signs that an injury has occurred. This noise, sometimes called pathological noise, can mean that something is wrong. However, Sometimes knee injuries can be mild, but they can also be severe enough to require surgery. You won't know for sure until a doctor looks at your knee.

Symptoms of Pop in the Knee

The knee is a strong and complex joint, but it has a very limited range of motion. As an articulated joint, it can only bend in one direction, leaving its structures very susceptible to being pushed out of place if hit or twisted. 

A "pop" is the sound of ligaments tearing or cartilage breaking. Small pieces of torn cartilage floating freely inside the knee joint can also cause catching and cracking.

Knee injuries are a major concern for athletes, but there are effective treatments and therapies available should an injury occur. The feeling of cracking in the knee can be described as follows:

• An audible "pop": You may feel a sudden tear in or around the knee during exercise and hear a pop at the same time.

• Sharp stabbing pain in knee comes and goes

• Sudden, severe pain: Pain that prevents normal movement of the knee joint may occur.

• Weakness and instability in the knee: You will likely be unable to bear weight on the affected knee.

• Bruising and swelling

• A catching, locking sensation

When to Consult a Doctor

A person should consult a doctor about a loud pop in the knee followed by pain, if:

• They feel pain and notice swelling

• They cannot move the joint easily

• The symptoms have not improved within a few days

• They cannot relieve the pain with over-the-counter pain relievers

• There is discoloration or numbness in the knee

• They cannot stand or put weight on the knee

When Is it Most Likely to Occur?

This injury is likely to occur in the following situations:

• Playing fast-paced sports: Sports involving sudden starts stops and turns often result in knee injuries. You may also feel pain behind knee due to this.

• Lifting heavy objects: This puts extra strain on the knee joint if proper lifting technique is not used.

Is a Pop in the Knee Serious?

Depending on how much pain you have or how limited your mobility is, you should have a good idea of ​​the severity of your injury. However, it can be further evaluated according to the following details.

• Not serious: An air bubble within the knee joint can form from time to time. Eventually, the bubble pops, which is painless, harmless, and just like cracking your knuckles.

• Moderately serious: A knee ligament may be hyperextended (overstretched) but only partially torn through.

• Serious: A knee ligament and/or a meniscus (cartilage on the sides of the knee) is completely torn through.

Causes of a Loud Pop in the Knee that’s Followed By Pain

Bouncing in the knee is usually harmless unless accompanied by pain or swelling. The sound and sensations tend to occur due to the structure of the knee. The knee consists of three bones:

• Kneecap called patella

• The leg bone called the tibia

• The thigh bone called the femur

The kneecap sits in the curvature of the thigh bone called the trochlea. When the knee straightens or bends, the patella moves back and forth inside the trochlea. The trochlea is padded with soft tissue for protection.

When a popping knee is accompanied by swelling, pain, or both, it may indicate an injury to the tissues—soft tissue or bone—surrounding the knee. If you suddenly hear a noticeable popping sound coming from your knee, it's pretty safe to assume that something is wrong, although the degree of injury can vary. Here are some of the possible causes.

• ACL Tear

One of the hallmarks of an anterior cruciate ligament (ACL) tear in the knee is a loud popping sound that is usually followed by intense pain. You may not be able to stand or put weight on the affected leg.

• PCL Injury

Your ACL isn't the only knee ligament that can get injured. However, posterior cruciate ligament (PCL) injuries at the back of the knee joint are less common than ACL injuries. It's also less likely than an ACL tear to cause the same kind of loud popping noise at the time of injury. You will likely experience some pain and swelling.

• MCL Injury

A tear of the medial collateral ligament (MCL) in the knee can also cause quite severe pain and swelling, and there can be an audible popping sound when the ligament is torn. The pain can vary depending on whether you are stretching it or tearing it. Later, you will likely feel some swelling and stiffness, possibly an inability to bend and straighten the knee.

• LCL Injury

The last of the four major ligaments in the knee, the lateral collateral ligament (LCL) is a relatively frequently injured ligament. However, it can be injured along with another ligament in the knee, so while you may hear a popping or popping sound if it is torn, it could also be the sound of another ligament. You will feel pain, weakness, and possibly numbness or stiffness.

• Meniscus Tear

A sudden twist or rotation or direct pressure can tear one of the two pieces of cartilage inserted between the femur and tibia. This type of injury, known as a meniscus tear, can cause cracking. However, Pain, swelling, difficulty moving, and a feeling of instability may follow. You may also feel a strange sliding sensation if the cartilage loosens and blocks the knee joint.

• Cartilage Injury

If a piece of cartilage becomes damaged, it may make a popping sound when the knee moves.

• Patellar Tendon Tear

Your patellar tendon connects the top of your tibia to the top of your kneecap. It can become inflamed, known as patellar tendonitis, or it can tear.

If it is tearing, you may hear a tearing or cracking sound. You may not be able to straighten your leg and your kneecap may feel like it is moving up into your thigh. You may also develop some pain, cramping, bruising, and an indentation at the base of your kneecap.

Pop-in-the-Knee Treatments and Relief

As long as you don't have severe loud pop in your knee followed by pain and still use the knee, treatment can begin at home while you see a doctor. You will likely need to undergo a consultation and follow-up examinations of your injury to prevent further complications.

At-home Treatments

When treating an injured knee at home, you can try the following to hopefully provide relief or prevent future injuries.

• Rest, Ice, Compression, and Elevation (RICE): When the injury first occurs, you can try resting the knee, icing the knee, compressing the knee with a bandage, and keeping the knee elevated, as shown by the RICE mnemonic. You can ice the area for 20 minutes at a time, turning it on and off as you see fit. You can also use over-the-counter pain relievers such as ibuprofen (Motrin/Advil) or other NSAIDs.

• Build Strength: You should always stretch and warm up before exercising. Try to strengthen your legs as much as possible in preparation for sports, such as extra practice or off-season training (if applicable), as strong muscles help protect and support the skeletal structure. You should also learn proper techniques for running, jumping, and landing.

• Wear The Right Sports Equipment: You should wear the right supportive footwear and avoid using cleats or spikes unless necessary. Make sure sports equipment, such as skis or skates, is properly adjusted.

Medical Treatments for Loud Pop in Knee Followed by Pain

In the following cases, you should see a doctor as soon as possible.

• Moderate injury: This means an injury that follows a painful burst but still allows some movement and walking.

• Recommendation for physical therapy: This will help with rehabilitation, including possible temporary use of a knee brace and crutches.