What’s That Noise In My Knee?

Joanne Halbrecht, MD

Is your knee crunching, grating, popping or snapping?  This may be a serious problem…or not.  Noise in the knee joint most often occurs with squatting, kneeling, going up and downs stairs and pivoting. The crunchy, grating, gravel noise is known as crepitus.

There are two primary sources of crepitus in the knee:

1. Worn cartilage on the patella (knee cap), tibia (shin bone) or femur (thigh bone). This worn cartilage is called chondromalacia and represents an arthritic change or breakdown of the cartilage. Normal cartilage looks like the smooth white stuff at the end of a chicken bone. In the early stages of osteoarthritis, cartilage becomes soft. Later on, it begins to break down; fissures or ravines form. Then, the cartilage starts looking more like crabmeat where it becomes frayed and breaks apart. Finally, the cartilage completely wears away and the bone is exposed. Rough or worn cartilage makes noise particularly when going up and down stairs, squatting or kneeling.
2. Scar tissue in the fat pad. There is a pad of fat just below the patella called Hoffa’s fat pad. In athletes who have participated in impact sports such as running or soccer, Hoffa’s fat pad, which is normally soft and mobile, can become hard due to scar tissue.

Treatment of crepitus in the knee depends on whether or not it is associated with pain. More commonly, chondromalacia is painful whereas scarring of the fat pad is not. Treatment of chondromalacia includes physical therapy, avoiding weight-bearing activities where the knee is bent more than 90 degrees such as lunges and leg presses, NSAIDs such as Aleve ®, or injections such as hyaluronic acid (HA), steroid or platelet rich plasma (PRP). Studies have shown that cell therapy (using your own fat or bone marrow) can also relieve pain in osteoarthritis. Occasionally, arthroscopic surgery is recommended to remove unstable cartilage or remove part of the fat pad. In severe cases of osteoarthritis unresponsive to conservative treatment, a knee replacement is indicated.

Popping and snapping have two common sources:

1. Medial parapatellar plica, known as Plica Syndrome. The plica is a structure found just to the inside or medial side of the patella (knee cap). It is a fold of tissue that can vary in size. Small plicas tend not to become problematic, but a larger plica can become inflamed with activity such as running, hiking and kneeling. The inflamed plica snaps when it is caught between the patella and femur when the knee is bent and can be painful.

2. Meniscus tear. The meniscus is a cartilage cushion in the knee between the tibia and femur. It serves as a shock-absorber and protects the cartilage on the surface of the bone from excessive wear and tear which can lead to chondromalacia or arthritis. When the meniscus is torn, it can pop or snap particularly with pivoting, squatting or kneeling. Symptoms of a meniscus tear typically wax and wane depending upon activity. Cycling and walking tend not to be painful, whereas running, pivoting and walking down stairs cause pain.

Treatment of Plica Syndrome includes use of NSAIDs, ice and physical therapy. Rarely, surgery is needed to remove the plica. A meniscus tear in a child may heal on its own depending on the location and extent of the tear. A meniscus tear that causes popping and snapping in an adult is typically treated with arthroscopic surgery to remove or repair the torn meniscus. Activities such as squatting, kneeling, pivoting and impact sports can cause the tear to become larger and necessitate removal of a large portion of the meniscus which can than lead to early arthritis.

Whether the knee pops, cracks, grinds or snaps, it is beneficial to seek early medial evaluation in order to avoid the need for surgery, relieve pain and recover more quickly.