Nuns Knee: Understanding Prepatellar Bursitis, Causes, Symptoms, and Treatment

What is Nuns Knee?

Nuns Knee, scientifically known as prepatellar bursitis, is an inflammation of the bursa located directly in front of the kneecap (patella), commonly caused by repetitive or prolonged kneeling, direct trauma, or infection.

Understanding Prepatellar Bursitis (Nuns Knee)

The human body contains numerous small, fluid-filled sacs called bursae (plural of bursa). These sacs act as cushions between bones, tendons, muscles, and skin, reducing friction during movement. They are essential for smooth, pain-free joint articulation.

The prepatellar bursa is strategically positioned between the skin and the front of the kneecap (patella). Its primary role is to allow the skin to glide smoothly over the patella as the knee bends and straightens, particularly during activities that involve kneeling.

The colloquial term "Nuns Knee" originates from the historical observation that individuals, such as nuns, who spent significant time kneeling in prayer or other duties, were prone to developing this condition due to the chronic pressure and friction on the prepatellar bursa. It is also known by other names like "Housemaid's Knee" or "Carpet Layer's Knee" for similar occupational reasons.

Causes and Risk Factors

Prepatellar bursitis typically arises from one of the following mechanisms:

• Repetitive Trauma or Prolonged Pressure: This is the most common cause.
  • Chronic kneeling: Occupations like carpet laying, plumbing, gardening, roofing, or even prolonged prayer.
  • Repetitive friction: Activities that involve constant rubbing over the kneecap.
• Acute Injury:
  • A direct blow or fall onto the kneecap can cause the bursa to become inflamed and swell with fluid.
• Infection (Septic Bursitis):
  • Bacteria can enter the bursa through a cut, scrape, or puncture wound over the kneecap. This is a more serious form requiring immediate medical attention.
  • The infection can also spread from other parts of the body via the bloodstream, though this is less common.
• Underlying Medical Conditions:
  • Systemic inflammatory conditions such as rheumatoid arthritis, gout, or pseudogout can predispose individuals to bursitis.

Signs and Symptoms

The symptoms of Nuns Knee can vary in severity but typically include:

• Swelling: A noticeable, often soft, lump or puffiness directly over the kneecap. This is often the first and most prominent symptom.
• Pain: Localized pain over the front of the kneecap. The pain often worsens with kneeling, direct pressure, or bending the knee.
• Tenderness: The area over the bursa will be tender to the touch.
• Redness and Warmth: If the bursa is inflamed, the skin over it may appear red and feel warm to the touch. These signs are particularly strong indicators of infection (septic bursitis).
• Limited Range of Motion: While the knee joint itself may function normally, pain and swelling can make full flexion (bending) of the knee uncomfortable or difficult.
• Fever and Malaise: In cases of septic bursitis, systemic symptoms like fever, chills, and general feeling unwell may be present.

Diagnosis

Diagnosing Nuns Knee (prepatellar bursitis) typically involves:

• Clinical Examination: A healthcare professional will visually inspect the knee for swelling, redness, and warmth, and gently palpate (feel) the area to assess tenderness and the nature of the swelling. They will also assess the knee's range of motion.
• Medical History: The doctor will ask about your occupation, hobbies, recent injuries, and any other medical conditions you may have.
• Imaging Studies (Optional):
  • X-rays: Primarily used to rule out other conditions like fractures or arthritis, as bursitis itself does not show on X-rays.
  • Ultrasound or MRI: Can be used to confirm fluid collection within the bursa and rule out other soft tissue injuries, though they are not always necessary.
• Fluid Aspiration (Bursa Aspiration): If infection (septic bursitis) is suspected, a small needle may be used to draw fluid from the bursa. This fluid is then sent to a laboratory for analysis to identify bacteria, white blood cell count, and crystal analysis (to check for gout). This is crucial for guiding treatment.

Treatment and Management

Treatment for Nuns Knee depends on the cause and severity of the condition.

Conservative Management (Non-Septic Bursitis):

Most cases of non-infected prepatellar bursitis respond well to conservative measures:

• RICE Protocol:
  • Rest: Avoid activities that aggravate the knee, especially kneeling.
  • Ice: Apply ice packs to the affected area for 15-20 minutes several times a day to reduce swelling and pain.
  • Compression: Use a compression bandage or sleeve around the knee to help reduce swelling.
  • Elevation: Elevate the leg above heart level when resting.
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Over-the-counter medications like ibuprofen or naproxen can help reduce pain and inflammation.
• Activity Modification: Avoid kneeling whenever possible. Use knee pads when activities require kneeling.
• Physical Therapy: Once acute symptoms subside, a physical therapist can provide exercises to maintain knee flexibility, strengthen surrounding muscles, and improve overall biomechanics to prevent recurrence.
• Corticosteroid Injections: In persistent non-septic cases, a corticosteroid injection directly into the bursa can help reduce inflammation and pain. This is usually performed after aspiration if infection has been ruled out.

Management of Septic Bursitis:

Infected prepatellar bursitis is a more serious condition requiring prompt medical intervention:

• Antibiotics: Oral or intravenous antibiotics are prescribed to fight the bacterial infection. The specific antibiotic chosen depends on the type of bacteria identified.
• Drainage: The infected fluid may need to be repeatedly aspirated (drained with a needle) or, in some cases, surgically incised and drained.
• Hospitalization: Severe or unresponsive cases of septic bursitis may require hospitalization for intravenous antibiotics and monitoring.

Surgical Intervention (Rare):

Surgery to remove the bursa (bursectomy) is rarely necessary but may be considered for:

• Chronic, recurrent bursitis that does not respond to conservative treatments.
• Persistent septic bursitis that does not clear with antibiotics and drainage.

Prevention Strategies

Preventing Nuns Knee primarily involves minimizing direct pressure and repetitive trauma to the prepatellar bursa:

• Use Knee Pads: This is the most effective preventive measure for individuals whose work or hobbies involve frequent kneeling.
• Take Frequent Breaks: If prolonged kneeling is unavoidable, take regular breaks to stand, stretch, and relieve pressure on the knees.
• Vary Positions: Avoid staying in one kneeling position for too long.
• Maintain Good Body Mechanics: Ensure proper posture and weight distribution during activities.
• Address Underlying Conditions: Manage chronic inflammatory conditions like gout or rheumatoid arthritis to reduce the risk of bursitis flares.
• Promptly Treat Skin Abrasions: Clean and cover any cuts or scrapes over the kneecap to prevent bacterial entry and potential infection of the bursa.

Prognosis

The prognosis for Nuns Knee (prepatellar bursitis) is generally good. Most cases of non-septic bursitis resolve with conservative treatment within a few weeks to a few months. Septic bursitis also typically resolves with appropriate antibiotic treatment and drainage, though it requires more urgent medical attention to prevent complications. Recurrence is possible, especially if preventive measures are not consistently followed.