The knee is a complex joint, subjected to various forces daily. Pain on the side of the knee, specifically the lateral aspect, is a frequent complaint that can impact mobility and quality of life. Understanding the diverse origins of this discomfort is an important first step toward addressing it effectively.
Understanding Lateral Knee Pain
Lateral knee pain is discomfort on the outer side of the knee. This region encompasses anatomical structures that provide stability and movement, including ligaments like the lateral collateral ligament (LCL), and tendons such as the iliotibial band and the biceps femoris tendon.
The lateral meniscus, a C-shaped piece of cartilage, also resides in this outer compartment, acting as a shock absorber. Additionally, bursae, small fluid-filled sacs, reduce friction between tissues.
Common Causes of Outer Knee Pain
Iliotibial Band (IT Band) Syndrome is a frequent cause of outer knee pain. It typically presents as a sharp or burning sensation on the outside of the knee, often intensifying around 30 degrees of knee flexion. It commonly affects runners and cyclists due to repetitive knee bending and extending, which can cause the iliotibial band to rub against the lower outer edge of the thighbone, leading to inflammation.
Another common issue is a lateral meniscus tear, which involves the cartilage cushioning the knee joint. These tears often result from twisting injuries or gradual wear and tear. Symptoms can include pain, swelling, a clicking or popping sensation, and sometimes a feeling of the knee locking or giving way.
A Lateral Collateral Ligament (LCL) sprain or injury also causes pain on the outer knee. The LCL connects the thigh bone to the shin bone, preventing the knee from buckling outward. Injuries usually occur from a direct blow to the inside of the knee, pushing the knee outwards, or from twisting movements during sports. Symptoms include pain, tenderness, swelling, and a feeling of instability in the knee.
Other Potential Sources of Lateral Knee Discomfort
Popliteus tendinopathy, an inflammation of the popliteus tendon, can cause pain in the posterolateral (back and outer) aspect of the knee. This condition is often aggravated by activities involving repetitive knee bending and extension, such as downhill running or deep squats. Overuse, poor foot biomechanics, or muscle imbalances can contribute to its development.
Biceps femoris tendinopathy, affecting a hamstring tendon, typically results in pain near its attachment on the fibular head, located on the outer side at the back of the knee. This overuse injury is common in athletes with repetitive running, sprinting, or sudden changes in direction. Symptoms include pain, tenderness, and stiffness, often worse with activities that use the hamstring muscles.
Lateral compartment osteoarthritis is a degenerative joint disease where cartilage on the outer side of the knee gradually wears away. While less common in isolation than medial compartment osteoarthritis, it causes aching pain, stiffness, and sometimes a grating sensation, especially with activity. Factors like age, previous knee injuries, or improper joint alignment can increase the risk of developing this condition.
Pain in the knee can sometimes originate from other areas of the body, known as referred pain. For example, issues in the hip or lower back, such as a pinched nerve or arthritis, can manifest as knee discomfort due to interconnected nerves. The pain from these distant sources tends to be achy, dull, and may migrate, often not radiating below the knee when originating from the lower back.
When to Consult a Healthcare Professional
Consult a healthcare professional if knee pain is severe or has a sudden onset, particularly after a forceful impact or injury. Seek medical attention if there is an inability to bear weight on the affected leg or to walk normally. Significant swelling, bruising, or a noticeable deformity of the knee also indicate a need for prompt medical evaluation.
Other concerning symptoms include a “popping” sound at the time of injury, or a feeling of the knee locking, catching, or giving way. If the pain worsens, does not improve with rest and self-care over a few days, or interferes with daily activities and sleep, a medical appointment is warranted. Numbness, tingling, or weakness in the leg or foot accompanying knee pain also signals a need for professional assessment.