A noticeable protrusion or swelling in the area just below the kneecap, often referred to as a “bump below the knee,” can be a source of concern. While many of these bumps are benign and resolve without extensive intervention, understanding their potential origins is helpful. This article provides general information about common reasons for such a bump and is not a substitute for professional medical advice.
Common Reasons for a Bump
One frequent cause of a bump below the knee is Osgood-Schlatter disease, common in growing adolescents. This condition involves inflammation of the patellar ligament where it attaches to the tibial tuberosity, a bony bump just below the kneecap. It often affects children and teenagers during growth spurts, particularly those in sports requiring running, jumping, and swift changes of direction. Pain and swelling typically subside once the child’s bones stop growing and growth plates harden.
Another common issue is patellar tendonitis, often called “jumper’s knee,” which results from overuse or repeated stress on the patellar tendon. This stress can create tiny tears in the tendon that connects the kneecap to the shinbone. Symptoms include pain, tenderness just below the kneecap, and stiffness, particularly when jumping, running, or kneeling.
Bursitis, specifically infrapatellar bursitis, can also lead to a bump below the knee. Bursae are small, fluid-filled sacs that cushion joints and reduce friction between tissues. When the infrapatellar bursa, located just beneath the kneecap, becomes inflamed, it can cause a soft, fluid-filled bump, along with pain, swelling, and warmth in the area. This inflammation often arises from repetitive kneeling, direct trauma, or overuse of the knee joint.
Other growths can also cause a bump. Ganglion cysts are non-cancerous, fluid-filled lumps that frequently form near joints or tendons, varying in size and texture. Lipomas, benign fatty tumors located just under the skin, present as soft, movable, and generally painless bumps.
Trauma or injury to the knee can directly result in a noticeable bump. A direct blow or fall can cause swelling, a hematoma (a collection of blood outside blood vessels), or a bone bruise, all of which manifest as a visible protrusion. These types of bumps usually appear suddenly after an incident.
In some instances, bony outgrowths called bone spurs, or osteophytes, can form. These develop on the edges of bones, often in response to joint degeneration, such as osteoarthritis, or wear and tear. While often asymptomatic, bone spurs can cause pain, stiffness, and a reduced range of motion if they interfere with joint movement or press on nerves.
Less commonly, an osteochondroma, a benign bone tumor, can cause a bump. This growth appears as a bony projection near a growth plate, most often around the knee or upper arm. While usually painless, it can cause discomfort, numbness, or tingling if it irritates nearby tendons or nerves. These growths typically stop developing once a person reaches skeletal maturity.
When to Seek Medical Advice
While many knee bumps are not serious, certain signs indicate that medical evaluation is appropriate. If the bump below your knee is accompanied by persistent or worsening pain, it warrants attention. A rapid increase in the bump’s size or its continued growth should also prompt a visit to a healthcare professional.
Signs that warrant medical evaluation include:
- Redness, warmth, or a fever accompanying the bump.
- Difficulty bearing weight, inability to walk normally, or limited knee range of motion.
- Numbness or tingling in your leg or foot.
- Bump appeared after a recent injury or trauma.
- Bump feels hard, fixed in place, or has an irregular shape.
- General unwellness alongside the bump.
How Doctors Diagnose and Treat
A healthcare professional begins the diagnostic process for a bump below the knee with a thorough physical examination. During this, the doctor assesses the bump’s size, tenderness, mobility, and any associated skin changes. They also take a detailed medical history, asking about symptom onset, activities that worsen or alleviate discomfort, and past injuries.
Imaging tests may be ordered to understand the underlying cause. X-rays can help identify bone-related issues like bone spurs or osteochondromas. Magnetic Resonance Imaging (MRI) provides detailed images of soft tissues, useful for evaluating tendons, ligaments, and fluid-filled structures. An ultrasound can also visualize fluid collections or other soft tissue abnormalities.
Treatment approaches vary depending on the diagnosis. Conservative management is often the initial step, including the R.I.C.E. protocol: Rest, Ice, Compression, and Elevation. Over-the-counter pain relievers, such as NSAIDs (ibuprofen or naproxen) or acetaminophen, are recommended to manage pain and reduce inflammation.
Physical therapy plays a significant role in rehabilitation, especially for Osgood-Schlatter disease and patellar tendonitis. A physical therapist designs programs focused on stretching and strengthening to improve muscle balance, range of motion, and knee stability. For persistent inflammation, like bursitis, corticosteroid injections may reduce swelling and discomfort. Surgical intervention is generally reserved for severe cases unresponsive to conservative treatments, or for specific conditions requiring removal. The ultimate treatment plan is tailored to the individual’s needs.