Overuse of your knee during sports or other activities that require frequent knee bending can irritate or injure your knee joint and cause pain on the outside of your knee. Back or hip pain that travels to your knee, years of normal wear and tear, and traumatic injury are other causes of outside knee pain. Problems with your knee cartilage, ligaments or bones can lead to outside knee pain. Treatment depends on the underlying cause of your pain.
Iliotibial Band Syndrome
Overuse syndromes are caused by activities that involve repeated knee bending, such as running and cycling. The most common is iliotibial band syndrome, in which outside knee pain develops when the iliotibial band -- a strip of tissue running along the outside of your leg from your knee to your pelvis -- becomes irritated when it repeatedly rubs against the outside of your knee bone. The pain from this syndrome typically worsens when walking up or down an incline. Unbalanced thigh muscle strength, inadequate stretching, poor training, inappropriate footwear and flat feet are some of the factors that contribute to developing an overuse syndrome.
Patellofemoral syndrome, also known as runner's knee, is an overuse syndrome in which an imbalance in the muscles that influence the position of the kneecap cause it to become misaligned and rub against the end of your thigh bone. Normally associated with pain at the front of the knee, this syndrome can also cause outer knee pain when your kneecap rubs against the outside of the bone. Pain usually occurs during activities such as sitting with your knees bent, squatting, climbing stairs and jumping. This syndrome is more common in women than in men.
Osteoarthritis occurs when the articular cartilage -- the slippery material covering the ends of your bones that allows them to smoothly slide across each other -- wears out after years of wear and tear. As the cartilage wears away, your bones begin to grind against each other and become irritated, causing pain. When the cartilage on the outside of your knee wears out, it causes outside knee pain. Factors that contribute to osteoarthritis of the knee include obesity and previous knee injury. This condition often causes early-morning knee stiffness that improves as you move around, difficulty standing from a sitting position and difficulty climbing stairs. Other types of arthritis that affect the knee can also potentially cause outer knee pain.
Lateral Collateral Ligament Injury
Knee trauma, especially sports-related, can injure the knee joint ligaments -- the bands of tissue that connect your thigh bone to your lower leg bones -- and cause outside knee pain. The lateral collateral ligament connects the outside, or lateral, part of your thigh bone to your lower leg bones. This ligament can be sprained or torn when the inside of the knee is pushed toward the outside, causing the ligament to stretch. When this injury occurs, you may feel a snap and knee instability. This injury is often the result of a tackle in football or a car accident, although it can occur in other situations.
Lateral Meniscus Tear
Knee trauma can also injure the menisci -- the cartilage that cushions and stabilizes your knee. Outside knee pain commonly develops when you tear the lateral, or outside, meniscus in your knee. This can occur when your upper leg suddenly turns in one direction while your foot is planted in another. In addition to being painful, your knee may catch or lock, making it hard to straighten. Your knee may give out when you try to stand on it after this injury.
Other Causes of Outside Knee Pain
Pain in your lower back or hip sometimes travels to your knee, causing a burning or pins-and-needles type of pain on the outside of your knee. This is called referred pain. Less common causes of outside knee pain include strain of the muscles attached to the outside of your knee joint, injury or compression of the nerve or artery that runs along the outside of your knee, and stress fractures on the outside of the thigh bone or shin bone within your knee joint.
Next Steps and Medical Care
It's important to see your doctor if you experience frequent, persistent or worsening outer knee pain -- especially if it does not improve with a few days of rest or interferes with your ability to perform your usual activities. Depending on the cause of your pain, treatment may include a combination of therapies, such as rest, medication, physical therapy and knee bracing. In some cases, surgery might be needed.
Seek medical care right away if you cannot put weight on the affected knee, have worsening or severe pain, or suddenly develop intense pain after a fall, sports injury or accident.