Whether you’re a professional athlete, a weekend warrior, or an aging boomer like me, a painful popping sensation within your knee is a liability. It can not only lead to a fall, but also damage the joint surfaces and eventually cause arthritis.
The pop results when something inside the knee is momentarily caught between the moving bones and is then suddenly released. (Think of plucking a guitar string.) There are three common culprits:
1. The most common cause is a synovial flap or plica. Folds of the normally thin and pliant lining of the knee, when inflamed, can grow larger, thicker, and stiffer. The inflamed membrane can then get caught and stretched between the moving parts of the joint.
2. The tough, crescent-shaped meniscal cartilages that cushion and guide the knee are often torn by soccer, football, and basketball players doing sudden cutting or twisting maneuvers. But tears can also occur by degeneration, just from getting older. The meniscus tear, like the synovial flap, can displace and get caught between the moving femur and tibia, and then pop when suddenly released.
3. Loose bodies are little pieces of cartilage and/or bone. They are most often knocked out of a joint surface by trauma, fall out, or grow, like pearls, within the synovial membrane. Like the flaps and tears, these fragments can get caught between the bones.
Regardless of the cause, popping within the knee is always abnormal and needs to be addressed.
If you notice recurrent popping in your knee, especially if it’s painful, first STOP doing whatever causes the sensation. Rest the knee out straight and apply moist heat for 15 to 20 minutes three to four times a day. Take an over-the-counter anti-inflammatory like Advil or Aleve (provided you have no history of stomach problems). If you don’t get relief within a few days to a week, the popping is probably not from inflammation. Time to see an orthopaedist for diagnosis and treatment.