Runners Knee (Patellofemoral Pain), Causes and Symptoms

Runner’s knee, also known as patellofemoral pain, is one of the top injuries incurred by avid runners. The femur, or thighbone, rests on the patella, or kneecap. This ball-and-socket setup allows the knee to bend and straighten. When a person experiences runner’s knee, the kneecap has not tracked correctly and this in turn causes the socket of the thighbone to become irritated and painful. This injury is not exclusive to runners, but can also occur in people who frequently bend their knees, either for work or during exercise. This injury makes up 42% of all overuse injuries in athletes.

While anyone can get runner’s knee, it is seen more commonly in women than men. The most common time of life when a person experiences runner’s knee is middle age, after the person has spent years overusing the joint and causing irritation. Also, according to the journal Gait and Posture, studies show that as women age, their knees become more misaligned. This can also lead to runner’s knee in middle-aged women. 

Anatomy of the Knee
The knee is the joint that connects the thighbone and shinbone and allows the leg to bend. It consists of the following:

  • The Femur (thighbone)
  • The Tibia (shinbone
  • The Patella (kneecap)
  • Articular cartilage
  • Collateral ligaments
  • Cruciate ligaments

The knee works to stabilize the body. The thighbone connects to the top of the kneecap via ligaments that help hold it in place. As the joint gets overused, these ligaments may weaken and cause the kneecap to rub against the thighbone socket, causing friction and pain.

Types of Runner’s Knee
Runner’s knee can be divided into three main types of injury:

  • Patellofemoral Pain: This is when a dull ache occurs around the knee. It is caused by overuse and a misalignment of the knee. This is the most general form of runner’s knee.
  • Patellar Tendinitis: This type of injury affects the tendons around the knee that are used to help stabilize the body while walking or running. The injury occurs when the tendons become inflamed or irritated.
  • Chondromalacia Patella: This is caused by softening cartilage around the kneecap and is usually seen in younger people, ages 15-35, who perform sports activities, putting pressure on the softer cartilage.   

Causes of Runner’s knee
While it is difficult to say what specifically causes runner’s knee to occur, there are a few basic known causes:

  • Biological Misalignment: When the kneecap is located too high up on the leg, or does not track correctly with the femur bone, it can cause abnormal wear and tear on the joint. Over a number of years, as this joint is used more and more, it can wear down, causing patellofemoral pain.
  • Weak or Tight Thigh Muscles: If the thigh muscles are not strong enough to support the thighbone or are too tight and inflexible during movement, it can create unnatural friction on the joint.
  • Pronating While Running: If the feet pronate, or naturally go to one side, it can cause the knee to misalign and rub on the thighbone. To help stop this, runners are advised to wear shoes that will eliminate pronation and help train their bodies to run correctly.
  • Overuse: This is the most common cause. As runners continuously put pressure on their knee joints, the ability of the body to absorb shock is lessened and more friction is put on the knees and thighs.
  • Soft Cartilage: When the cartilage has not fully ossified, or become solid, it can cause the bones to rub against each other, creating friction and ultimately causing runner’s knee.

Symptoms of Runner’s Knee
Different people have different symptoms of runner’s knee. However, in all cases, there is pain in the knee joint that tends to worsen with activity. 

The following are common runner’s knee symptoms. Depending on the age and activity level of the person with this condition, these may vary:

  • Dull ache above or on the outside of the knee
  • Rubbing or clicking noise that can be heard and felt whenever the knee is bent or straightened
  • Tenderness to the touch

Runner’s knee symptoms occur mostly during activity, but can also occur after sitting for a prolonged period of time. The condition can also be associated with other symptoms in this delicate part of the body. For this reason, any person experiencing these symptoms should see a medical professional for help and immediately reduce the number of miles put on the knee.

The multidisciplinary team of orthopaedic experts at North Shore-LIJ Orthopaedic Institute's Trauma Services in New York treats Runner’s Knee (Patellofemoral Pain) as well as a broad range of conditions that affect the bones within the body.

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