As we get older, we feel new aches and pains, along with hearing new pops in our joints. Some of us crack our knuckles and don't think about it. When your knee pops, you hope it's just the joint releasing air and not something more. So, when do you need to worry about a knee pop?
Why Do We Hear a Pop?
The most common noise we hear is the air that builds and forms bubbles between the joints. When you stretch the joint, you'll hear a "pop" noise as it releases. There's no evidence that this causes any harm to the joints. So, most people just continue with their activity after hearing it. But a pop can also cause pain or mean something more.
The body has a lot of moving parts, literally. But for a pop to happen, you need bones, ligaments, and muscles. These body components can break or tear. When that happens, they create an audible noise.
ACL Tears: The Season-Ender Knee Pop
Orthopedic surgeon F. Winston Gwathmey Jr., MD, specializes in sports medicine. He shares that the anterior cruciate ligament (ACL) tear is the most noticeable knee pop that you won't be able to walk off. An ACL tear isn’t as common as other knee injuries, but it can still happen.
Most ACL tears are non-contact, meaning that nothing collides with the knee to cause the injury. Your knee needs to be in a certain position and receive the correct amount of force to tear the ACL. You may hear a pop and then you’ll feel it immediately. You'll fall to the ground as your knee gives out. It'll feel like someone tackled you. Since the ACL has a rich blood supply, the knee swells quickly and gets big.
Treatment for ACL Tears
ACL tears are more common in athletes, but they can happen while running on a trail or apple picking. "It's really an unlucky injury," Gwathmey shares. It all depends on the position of the knee when the injury occurs. Most ACL tears need surgery.
Once the swelling goes down, an orthopedic surgeon can reconstruct the knee by grafting a tendon into your knee, which becomes the new ACL ligament. Usually, they’ll take a tendon from the same knee. But they can also use one from a cadaver if your tendons are unhealthy. This isn't very common for younger, healthy patients.
ACL surgery is arthroscopic, meaning the surgeon makes only tiny cuts. This means you can go home the same day. The surgeon:
- Uses a tiny video camera to view the inside of the knee joint
- Drills tunnels in the thigh and shin bones
- Threads the new tendon
- Screws everything into place
After surgery, your knee will get stiff. Your doctors want you to get back to normal motion quickly, so you’ll start physical therapy immediately. The goal is to strengthen and build up the range of motion in your knee.
Recovery can take 6-9 months. Most players are back to their sport the following season.
Other Knee Pops
Knee sprains are another common, less serious knee injury. These sprains:
- Involve the medial collateral ligament (MCL), which runs along the inside of the knee
- Are more common with a contact injury
- Usually don’t make a noise
- Have less swelling than an ACL tear
- Usually heal without surgery
Gwathmey recommends rest and a brace to help stabilize your knee during recovery.
You can also dislocate your kneecap and tear the ligament that holds it in place. You'll likely fall awkwardly, and you'll notice your knee cap out of place. The knee gets stuck in a slightly bent position.
As awful as it sounds, straightening your leg should knock your knee cap back into place. If this doesn’t happen, you should call your provider or visit the emergency room.
And lastly, a posterior cruciate ligament (PCL) tear requires extreme force. You’re more likely to experience this during a car accident or football tackle. Doctors will consider the severity of the injury before choosing the best treatment option.
When Your Cartilage Is Damaged
A meniscus tear is a common injury as we age. As a C-shaped piece of cartilage, it’s the shock absorber within your knee. You can catch the edge of it or even tear it without necessarily feeling or hearing it. Afterward, you may notice:
- A reproducible pop in your knee — Gwathmey describes it as a pinch-and-pull feeling
- Pain or clicking in the joint, as the free-floating cartilage irritates your knee
- Slow swelling, over 3-5 days
The treatments vary depending on the type of tear. In some tears, the blood supply is tenuous and the surgeon will clip out the meniscus fragment. In other tears with better healing potential, they may try to fix it with stitches.
With clipping, most people are back to enjoying normal activities within 4-6 weeks. Repair recovery can take much longer, between 4-6 months. The healing process is hard, as the meniscus doesn't get a lot of blood supply.
Cartilage is a slippery substance between your bones. It helps them glide without digging into each other as you move. Damaged cartilage can create friction or mechanical symptoms as the knee moves. Worn out cartilage results in osteoarthritis.
When To Consider Surgery
Severe arthritis pain? It might be time for knee replacement surgery.
Osteoarthritis, when you damage all your cartilage, can also cause knee pops. The wear and tear from high-force impacts or injuries can break down the bone's cushion. You may want to consider a knee replacement if pain continues after medication and other treatment options.
How to Avoid a Knee Injury
Your cartilage loves motion. It receives its nutrition from the fluid inside the knee, and motion encourages joint health. When you're sitting all day, it's not getting enough nutrition to stay healthy. Just like you, it needs a healthy lifestyle.
A well-balanced diet with protein, vitamin D, and calcium helps keep your bones and knees healthy. But smoking puts you at a higher risk for osteoarthritis. It restricts your blood flow, which can cause damage to your cartilage.
Keep your muscles strong, especially your quads. The muscles around your knee can balance impact and lower your risk of a major injury. If you do get injured, your physical therapist will concentrate on your hamstrings and quads while your knee recovers.
There are a lot of moving parts involved with your knee. If you hear a pop but there’s no swelling or pain, don't worry about it. Do see a doctor if there’s:
- A sense of instability
The Right Exercise
There's no evidence that overuse can damage your cartilage, but we know forceful impacts can. So Gwathmey recommends low-impact exercises like:
- Using an elliptical machine
- Pool workouts — try running in the water
Love running? Running long distances every day can result in the accumulation of microtrauma. Your knee may need some time to heal between runs. Try to alternate your routine. You can run in a different location so your knee sees a different motion. But ideally, run every other day. In between, swim or ride a bike for exercise.