There are many causes of outer knee pain or pain on the side of the knee facing away from the body. According to the U.S. National Library of Medicine and the National Institutes of Health (NIH), knee problems can cause significant pain and affect a person's activities of daily living. The NIH states that the knee is composed of or stabilized by bone, cartilage, muscles, tendons, ligaments and fluid, and that if any of these structures are injured or diseased, knee problems--including outer knee problems--can manifest.
Iliotibial Band Syndrome
Iliotibial band syndrome can cause outer knee pain. According to the Sports Injury Clinic website, iliotibial band syndrome, also known as iliotibial band friction syndrome, occurs with repetitive rubbing of the iliotibial band--a thick sheath of fibrous connective tissue that runs along the outside of the thigh, from the hip bone and the tensor fascia lata muscle to the outer aspect of the tibia or shin bone--over the lateral femoral condyle, a bony prominence on the outside aspect of the knee.
Repetitive knee flexion and extension, which occurs during activities such as running, can cause the tissues composing the outer knee to become inflamed or irritated. Common signs and symptoms associated with iliotibial band syndrome include: pain on the outside of the knee, iliotibial band tightness, knee pain that's made worse by running, pain with knee flexion and extension, weakness with hip abduction or moving the leg away from the body's midline and tender points in the gluteal muscles.
Lateral Collateral Ligament Sprain
A lateral collateral ligament sprain can cause outer knee pain. The NIH states that a lateral collateral ligament injury typically involves a stretch, partial tear or complete rupture of the lateral collateral ligament--the principle ligament that stabilizes the outside aspect of the knee. The lateral collateral ligament runs from the top of the fibula--the smaller of the two bones in the shin or lower leg--to the bottom of the femur or thigh bone. This ligament is responsible for maintaining lateral stability in the knee joint.
The most common mechanism of injury of the lateral collateral ligament is force applied to the inside aspect of the knee joint, which places significant stress on the tissues of the outer knee, including the lateral collateral ligament. According to the NIH, common symptoms associated with a lateral collateral ligament sprain include: knee instability, outer knee pain or tenderness and knee swelling.
Lateral Meniscus Tear
A lateral meniscus tear can cause outer knee pain. According to Cedars-Sinai Medical Center (CSMS)--a nonprofit hospital and academic medical center in Los Angeles, California--the menisci are crescent-shaped bands of cartilage in the knee that attach to the tibia and serve as shock absorbers and knee stabilizers. Each knee has two menisci, including a medial meniscus and a lateral meniscus. Both menisci are located within the knee joint, although the medial meniscus is situated on the inside aspect of the knee joint, whereas the lateral meniscus is situated on the outer aspect of the knee joint.
The CSMC states that meniscus tears can vary considerably in size and severity. Common signs and symptoms associated with a lateral meniscus tear include: an inability to extend the knee without discomfort, pain that develops gradually over the lateral knee joint line and knee swelling, stiffness and tightness.
