15 Common Causes of Knee Pain Sorted by Location

By Dr. Jeffrey Peng, MD · Published March 5, 2026 · 8 min read

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Knee pain is not random. Where you feel the pain can serve as a powerful diagnostic clue to the underlying problem. By understanding the source of your symptoms, you can take the appropriate first steps toward recovery.

As a board-certified sports medicine physician, I evaluate knee pain every day in my clinic. In this guide, I walk through 15 of the most common causes of knee pain, organized by location — from above the kneecap all the way to the back of the knee. Think of it as a map to help you identify what may be going on with your knee.

What Causes Pain Above the Kneecap?

The area above the kneecap is where the quadriceps — the large thigh muscle — transitions into the quadriceps tendon and attaches to the patella. Repetitive stress or chronic overloading of this tendon can contribute to its degeneration, a condition known as quadriceps tendinopathy. Mechanical stress at the tendon's attachment point can also produce bone spurs called enthesophytes.

The good news is that quadriceps tendinopathy responds well to a structured exercise and rehabilitation program designed to support and strengthen the area. Physical therapy is often all that is needed to resolve symptoms.

What Causes Pain Around or Behind the Kneecap?

Pain around or behind the kneecap is most often caused by patellofemoral pain syndrome, also known as runner's knee. This condition typically arises from imbalances or abnormal tracking of the patella, which leads to irritation and inflammation underneath the kneecap. It is almost always driven by a combination of biomechanical problems — muscle imbalance, poor patellar alignment, or foot issues such as flat feet.

Identifying and correcting these biomechanical problems often leads to complete symptom resolution. A home exercise program or physical therapy is the standard treatment approach.

Patellofemoral arthritis can also cause pain behind the kneecap. Arthritis results from the deterioration or loss of the protective cartilage that cushions the bones. One key distinguishing factor is swelling: arthritis often leads to joint swelling, whereas patellofemoral pain syndrome does not.

What Causes Pain in Front of the Kneecap?

Pain in front of the kneecap — beneath the skin but above the bone — is frequently caused by prepatellar bursitis. A bursa is a small, fluid-filled sac designed to reduce friction and act as a cushion. Repetitive trauma or excessive pressure on the front of the knee can inflame this bursa, causing visible swelling and tenderness.

Ice, compression, and anti-inflammatory medications usually resolve prepatellar bursitis. In some cases, the fluid may need to be aspirated by a healthcare provider.

What Causes Pain Below the Kneecap?

Below the kneecap, the quadriceps tendon becomes the patellar tendon, which runs from the bottom of the patella to its insertion on the tibial tuberosity. Pain along this distribution is often caused by patellar tendinopathy — sometimes called jumper's knee. The patellar tendon plays a critical role in transmitting forces from the quadriceps to the lower leg during activities like jumping, running, and kicking. Like quadriceps tendinopathy, this condition can produce bone spurs and enthesophytes at the attachment site.

Patellar tendinopathy responds well to exercise therapy and structured rehabilitation.

Another cause of pain in this region is infrapatellar fat pad impingement. The infrapatellar fat pad is a cushion between the patellar tendon and the bony structures of the knee joint. When this fat pad becomes compressed, irritated, or inflamed, it produces discomfort at the front of the knee, typically behind or around the patellar tendon.

What Causes Pain on the Inside of the Knee?

To find the medial joint line, start at the inside edge of the patellar tendon and run your fingers back and forth as you move toward the inner aspect of the knee. You should feel a soft space between the two bones. Pain along this joint line is typically caused by medial compartment osteoarthritis, a medial meniscus tear, or often a combination of both.

Slightly above the joint line on the innermost aspect of the knee is where the medial collateral ligament (MCL) originates. This is where patients experience pain following an MCL sprain. The most common mechanism of injury is a sudden impact or blow to the outside of the knee, forcing it inward and stretching or tearing the ligament.

Pain below the medial joint line is usually caused by pes anserine bursitis. The pes anserine bursa sits between the tendons of the sartorius, gracilis, and semitendinosus muscles. Repetitive stress, overuse, and muscle imbalances lead to irritation and inflammation of this bursa. This condition is readily treated with an exercise and rehabilitation program.

What Causes Pain on the Outside of the Knee?

Using the same technique — starting at the outside edge of the patellar tendon and feeling for the soft space between the bones — you can locate the lateral joint line. Pain here is often due to lateral compartment arthritis, a lateral meniscus tear, or commonly a combination of both.

Pain above the lateral joint line is most likely due to iliotibial (IT) band syndrome. When the IT band is overly tight, it rubs against the underlying bone, causing friction and irritation. This then inflames a nearby bursa, producing bursitis and pain. Stretching, foam rolling, and addressing underlying biomechanical issues typically lead to symptom resolution.

Below the lateral joint line, near a bony prominence called the fibular head, runs the common peroneal nerve. This is a common location for nerve irritation. Compression can result from trauma, prolonged pressure, or repetitive activities like kneeling or crossing the legs. Symptoms may include pain, numbness, tingling, or even weakness of the foot and lower leg.

What Causes Pain Behind the Knee?

One of the most common causes of pain behind the knee is a Baker's cyst (also called a popliteal cyst). This is a fluid-filled sac that typically develops as a result of underlying knee pathology — such as arthritis, meniscus tears, or cartilage injuries. Inflammation inside the joint causes excess fluid production, which then accumulates in the back of the knee, forming the cyst.

Two Conditions That Can Cause Knee Pain Anywhere

Knee arthritis can produce pain and discomfort virtually anywhere in and around the knee — on the inside, the outside, around the kneecap, or behind the knee. Anywhere there is cartilage loss causing the bones to rub against each other will generate pain and symptoms. If you are dealing with knee arthritis, there are many effective non-surgical treatment options available, including PRP injections and structured exercise programs.

Myofascial trigger points are hyperirritable spots within muscle fibers that can be extremely sensitive to touch. Compressing, stretching, or loading the affected muscle reproduces pain and symptoms. They are typically caused by trauma or injury, poor posture, repetitive movements, or chronic muscle tension.

Trigger points can also restrict range of motion and cause weakness, leading to chronic pain and functional limitations. The most common trigger points affecting the knee include the vastus medialis oblique (VMO), which refers pain toward the inside and front of the knee; the vastus lateralis, which causes pain along the outer thigh and knee; and the gastrocnemius and hamstring muscles, which can produce pain behind the knee.

The tricky aspect of trigger points is that they are frequently overlooked and misdiagnosed. However, a growing body of evidence suggests that trigger points are among the most common causes of all musculoskeletal pain.

When Should You See a Doctor for Knee Pain?

If your knee pain is persistent, worsening, or accompanied by significant swelling, instability, locking, or difficulty bearing weight, it is important to see a healthcare provider for a thorough evaluation. A sports medicine physician can perform a focused physical examination, order appropriate imaging if needed, and develop a personalized treatment plan.

If you are in the San Francisco Bay Area and would like to discuss your knee pain, feel free to schedule a consultation.

Medical Disclaimer: This content is for educational purposes only and does not substitute for the medical advice of a physician. Always consult your healthcare provider before beginning any new treatment program. The information presented reflects the opinion of Dr. Jeffrey Peng and does not represent the views of his employers or affiliated hospital systems.