Uneven Kneecaps: Why One Patella Looks Larger and What to Do

In a healthy adult, the left and right patellae (kneecaps) are typically symmetrical in size and shape. A noticeable difference between the two knees is not normal and should prompt a clinical evaluation to determine the underlying cause.

Potential Causes of Patellar Asymmetry

• Trauma or Injury: Previous fractures, dislocations, or ligament tears (ACL, MCL) can lead to muscle atrophy (quadriceps wasting) or bony remodeling, making one kneecap appear smaller or the joint contour altered.
• Developmental Conditions: Congenital anomalies such as patellar hypoplasia (underdevelopment) or bipartite patella (a two-part kneecap) can create asymmetry.
• Inflammatory Arthritis: Rheumatoid arthritis or other inflammatory conditions cause joint swelling, effusion, and structural changes that can enlarge the appearance of the knee.
• Neurological Disorders: Conditions affecting nerve supply—such as polio, stroke, or spinal cord injury—can cause significant muscle wasting on one side, altering the contour around the patella.
• Tumors or Cysts: Rarely, benign growths (e.g., ganglion cysts, lipomas) or malignant tumors around the knee joint can cause visible enlargement.

When to Seek Medical Advice

Schedule an appointment with a healthcare provider if you notice:

• A visible size difference between the kneecaps
• Pain, swelling, or instability in the knee
• Limited range of motion
• A history of knee trauma or surgery

Important: Self-diagnosis based on online information is not recommended. A proper clinical examination, possibly including imaging (X-ray, MRI), is necessary to determine the underlying cause and appropriate treatment plan.