A bulge on the side of the knee can be concerning. While some indicate minor issues, others signal underlying conditions requiring medical attention. Understanding its characteristics and accompanying sensations helps identify its nature. This article explores potential causes, associated symptoms, diagnostic methods, and general management approaches for a side knee bulge.
Potential Causes of a Side Knee Bulge
A bulge on the side of the knee can arise from various structures within or around the joint, each with distinct characteristics. On the inner, or medial, side of the knee, pes anserine bursitis is a common cause. This involves inflammation of a fluid-filled sac (bursa) where three tendons attach to the shinbone, leading to localized swelling and tenderness.
Another medial cause is an injury to the medial collateral ligament (MCL), which can result in swelling following a sprain or tear. A medial meniscus cyst, a fluid-filled sac linked to a tear in the medial meniscus cartilage, can present as a firm, sometimes movable, lump.
On the outer, or lateral, side of the knee, iliotibial (IT) band friction syndrome can manifest as localized swelling. An injury to the lateral collateral ligament (LCL) may also cause swelling and a bulge, similar to MCL injuries. A lateral meniscus cyst, analogous to its medial counterpart, is a fluid-filled sac associated with a tear in the lateral meniscus. Inflammation of the biceps femoris tendon or its adjacent bursa (biceps femoris tendonitis or bursitis) can also lead to swelling near the outer hamstring attachment.
Beyond specific medial or lateral structures, some causes can appear on either side. A popliteal cyst, often called a Baker’s cyst, typically forms behind the knee but can extend or rupture, causing swelling. These cysts are often associated with underlying knee joint issues, such as arthritis or meniscal tears.
Ganglion cysts, non-cancerous, fluid-filled lumps that form along tendons or joints, can develop around the knee. Less commonly, a lipoma, a benign fatty tumor, can present as a soft, movable lump beneath the skin. In rare instances, an osteochondroma, a benign bone growth, can cause a hard, fixed bulge near the bone’s growth plate.
Accompanying Symptoms and When to Seek Medical Advice
While a knee bulge is a symptom itself, other signs indicate the urgency of seeking medical evaluation. Pain, especially if severe, worsening, or constant, suggests a significant underlying issue that warrants attention. Redness, warmth, or fever alongside a bulge could signal an infection or severe inflammatory process requiring prompt medical assessment.
Rapid growth in the bulge’s size or a noticeable change in its appearance also serves as a red flag for medical consultation. Difficulty bearing weight or significant limitation in the knee’s range of motion indicates potential joint damage. Numbness or tingling in the leg or foot, particularly below the knee, may suggest nerve involvement or compression.
If the bulge appeared suddenly after an injury (e.g., fall or direct impact), medical evaluation is important to assess for ligament tears, fractures, or other acute trauma. If the bulge feels hard, is fixed, and does not move, it may indicate a bone-related issue or a complex mass that requires professional diagnosis. Any persistent or concerning knee bulge should be evaluated by a healthcare professional to ensure proper diagnosis and management.
How Doctors Diagnose a Knee Bulge
Diagnosing the cause of a knee bulge begins with a thorough medical history and physical examination. The healthcare provider will ask about the bulge’s onset, associated symptoms like pain or instability, and recent injury. During the physical examination, the doctor will inspect and palpate the bulge to assess its size, consistency (soft, firm, hard), mobility, and tenderness. They will also evaluate the knee’s range of motion, stability, and integrity of ligaments and menisci through specific maneuvers.
Following the initial examination, imaging studies visualize underlying structures. An X-ray identifies bone abnormalities or rules out fractures, though it does not visualize soft tissues well. Ultrasound assesses fluid-filled structures like cysts or inflamed bursae, and distinguishes between solid and cystic masses.
For a detailed view of soft tissues, including ligaments, tendons, menisci, and complex cysts, a Magnetic Resonance Imaging (MRI) scan is frequently used. If a fluid-filled cyst or bursa is suspected, aspiration (drawing fluid from the bulge with a needle) may be performed for diagnostic analysis and symptomatic relief.
General Approaches to Managing a Knee Bulge
Management of a knee bulge depends on the specific underlying diagnosis. For many inflammatory conditions or minor injuries, conservative management is the initial approach. This often includes applying the RICE protocol: Rest, Ice, Compression, and Elevation.
Over-the-counter pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs), can also help manage pain and inflammation. Physical therapy plays a role in rehabilitation, focusing on exercises to strengthen knee muscles, improve flexibility, and correct biomechanical issues. Modifying daily activities to reduce stress on the knee is also recommended.
When conservative measures are insufficient, medical interventions may be considered. These can include corticosteroid injections directly into an inflamed bursa or joint to reduce inflammation and pain. Aspiration, the draining of fluid from large cysts or bursae, can provide immediate relief.
For conditions like significant ligament or meniscus tears, persistent cysts, or symptomatic benign growths, surgical options may be discussed. Surgical intervention aims to repair damaged structures, remove problematic cysts, or excise growths that cause symptoms or functional impairment.