The knee is the largest joint in the body and it’s responsible for allowing the leg to bend and straighten. That means that a lot of stress is put on the area on a daily basis and it’s not surprising that it’s one of the most frequently injured parts of the body. In fact, most people will experience knee pain at some point in their lives. Here are a few of the most common causes of that pain:

Cartilage tear

Cartilage is the tough, flexible tissue that covers the ends of bones. It’s also what makes up the two menisci on either side of the knee: the medial meniscus and the lateral meniscus. The menisci are two of the most commonly injured parts of the knee, with those injuries occurring most often when the knee is forcefully twisted or rotated while the foot is planted. If an injury does occur, a popping, snapping, or clicking may be felt deep inside the knee, along with intense pain, especially when suddenly starting or stopping movement.


The cartilage that wraps around the ends of the knee bones allows those bones to rub against each other smoothly. When that cartilage wears away, however, there is nothing to buffer the grinding and bone rubs against bone, causing deep pain. This is known as arthritis. People tend to develop arthritis as they grow older since a wearing away of cartilage is a natural part of the body’s aging process. There are other factors, however, such as drastic weight fluctuations or obesity that can cause arthritis to occur in people of a young age.

Ligament injury

Ligaments connect your thighbone to your lower leg bone, keeping the bones together and helping to stabilize the knee. There are three ligaments in the knee: the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and medial collateral ligament (MCL). Ligaments can be strained, torn, or stretched and these injuries are often debilitating due to the fact that they cause the knee joint to become unstable.

Ligament injuries are common amongst athletes. The ACL, for example, is most often strained or torn when the foot is planted and the knee is twisted, a common movement in basketball. The PCL, on the other hand, is often injured by direct impact, making it an unfortunately common affliction for football players.

Muscle strain or tear

Just like any other place in the body, the muscles around the knee joints can be torn or strained, causing pain and tightness that occurs, most often, directly at the point of the strain. Additionally, muscle strain to the groin, quads, or hamstrings can also cause knee pain.


Tendinitis occurs when the tendons of the knee become inflamed, often due to overuse. Runners, cyclists, and dancers are some of the athletes most often affected by tendinitis, but in can occur any time an abundance of stress is repeatedly put on the knee. Tendinitis of the patellar tendon—often called “jumper’s knee”—for example, is common among basketball players and caused by muscle strain from the impact of jumping up and down repeatedly. Tendinitis will result in soreness in the area and a lump may develop along the tendon. The pain in the area will generally increase when the knee is moved or flexed.