Crepitus of the Knee (creaking knees)

Causes of crepitus

There are various causes of crepitus.

Air bubbles

The popping sound usually comes from air seeping into the soft tissue, finding its way into the area around the joint and causing tiny bubbles in the synovial fluid.

When a person bends or stretches their knees, the bubbles can burst with a popping or cracking sound.

This may sound alarming, but it is usually harmless.

Damage to the knee joint

Sometimes, however, there is an underlying problem, for example, tissue damage or lesions. In this case, treatment may be necessary.

If there is pain as the knee snaps or catches, it can be because scar tissue, a meniscus tear, or a tendon is moving over a protruding bone within the knee joint.

Pain or swelling can be a sign of a more serious problem, such as patellofemoral pain syndrome (PFS), a tear in the cartilage or other soft tissue, or osteoarthritis (OA).

These issues may need medical attention. Let's look at them now in more detail.

Patellofemoral pain syndrome

Crepitus of the knee refers to a cracking or popping sound or sensation in the knee joint.

When the pressure between the kneecap and the femur is greater than usual, the cartilage in the joint can start to soften and wear away.

As it loses its smoothness, it can lead to a condition called patellofemoral pain syndrome (PFS), or "runner's knee."

PFS can result from trauma or overuse. It can also result if a part of the person's knee is badly aligned. It is a common source of knee pain in young people and athletes.

Rigorous exercise — such as jogging on an inclined surface, squatting, and climbing stairs — can put strain on the area between the femur and the kneecap joint.

A sudden increase in physical activity, such as exercising more frequently, or running further or on rougher terrain than usual, can also cause it.

Another risk factor for crepitus related to PFS is trauma to the knee. This could be due to a fall or hitting the knee on the dashboard of a car in a road traffic accident.

The individual may experience crepitus when climbing stairs or after sitting for a long time with the knees bent, as well as pain, swelling, puffiness, and stiffness.

Treatment for PFS

The first line of treatment for this condition includes rest, ice, compression, and elevation, or "RICE."

Anti-inflammatory medication and physical therapy exercises can also relieve it.

If these do not help, splinting, surgery, or both may be necessary. They may help to realign part of the knee.

To prevent this problem, anyone who is exercising or participating in sports should make sure they always use appropriate techniques, footwear, and equipment, and be sure to warm up before starting.

Torn cartilage

Crepitus can also be a sign of a torn meniscus. A meniscus can tear during sports activities, such as when a person twists their knee. It can also happen as people get older and the meniscus wears thin.

Symptoms include:

• swelling

• stiffness

• difficulty extending the knee

The American Academy of Orthopaedic Surgeons (AAOS) explain that, when the meniscus tears, the individual may experience a "popping" sensation.

Normally, the person can still use the knee, but stiffness and swelling may appear over the next 2 to 3 days.

As with PFS, the first line of treatment is RICE and anti-inflammatory medication. Sometimes surgical repair is necessary.

Osteoarthritis of the knee

If crepitus occurs with pain, this can be an early sign of osteoarthritis (OA) of the knee. OA is normally a result of wear and tear, and it tends to develop and worsen with age.

In OA, the cartilage that covers the ends of bones in the joints gradually wears away. Bones rub on this increasingly rough surface, resulting in pain and mobility issues. It is more likely among people with obesity or those who have had an injury in the past.

A study published in the journal Osteoarthritis and Cartilage found that women aged 45 to 60 years who had both crepitus and patellofemoral pain had a 72 per cent chance of developing OA, although they did not yet have a diagnosis of OA.

The Centers for Disease Control and Prevention (CDC) estimate that 49.6 per cent of adults aged 65 years and above were living with a diagnosis of arthritis between 2013 and 2015.

Tips and treatment

If a person has an early diagnosis of OA, the Osteoarthritis Foundation suggest using nonsurgical options to slow the progression, maximize mobility, and improve strength.

Options include:

• lifestyle modifications, such as weight loss and exercise

• medication

• physical therapy

As OA progresses, treatment through medication or even knee replacement surgery may be necessary.

Crepitus following surgery or trauma

Research published in Clinics in Orthopedic Surgery shows that up to 18 per cent of people who have a total knee arthroplasty (TKA), or knee replacement, will experience crepitus. This may be due to the design and fit of the new knee.

This type of crepitus usually resolves without intervention.

However, if problems persist, a doctor may recommend debridement, a minor surgical procedure to remove debris from around the joint.

Another reason for crepitus after surgery is arthrofibrosis or the development of scar tissue. This can lead to pain and stiffness in the joint. It can also happen after a traumatic injury.

If the person experiences pain and stiffness after an injury or surgery, they should see a doctor. The doctor may recommend monitoring the knee, and it may need treatment.

Often, however, crepitus that follows an injury or surgery is not serious. Doctors suggest that, for some people, the crepitus may have been there before, but an increased awareness of how the joint is reacting makes it more noticeable now.

Often, say the researchers, reassurance and rehabilitation are enough.

Managing crepitus

Keeping physically active and warming up before exercise can help protect the knees.

Treatment may not be necessary. If it is, the options will depend on the cause, as outlined above.

If crepitus occurs with exercise, the person should not stop exercising but modify the exercise.

Precautionary measures include:

• avoiding inclines or hills if running

• when using a bicycle, keep the tension on the pedals low

• when lifting weights, focus on the quadriceps or hamstring muscle groups, use lighter weights and do more repetitions

When exercising, people should always listen to their body. If there is pain, they should stop. Always exercise in moderation and stretch before exercising.