Knee Bursitis: Understanding the Most Common Types, Causes, and Treatments

What is the most common bursa to get bursitis in the knee?

The most common bursa to experience bursitis in the knee is the prepatellar bursa, often referred to as "Housemaid's Knee" due to its superficial location and susceptibility to direct pressure and friction.

Understanding Knee Bursae: An Anatomical Overview

To truly understand knee bursitis, it's essential to first grasp the anatomy of bursae themselves. Bursae (plural of bursa) are small, fluid-filled sacs located throughout the body, acting as cushions between bones, tendons, muscles, and skin. Their primary function is to reduce friction and facilitate smooth movement, particularly around joints. The knee joint, being one of the body's largest and most complex, houses numerous bursae to accommodate its extensive range of motion and weight-bearing demands.

While there are many bursae around the knee, a few are particularly relevant to the development of bursitis due to their superficial location or high exposure to stress and friction. These include the prepatellar, infrapatellar (superficial and deep), pes anserine, and iliotibial band (ITB) bursae.

The Most Common Culprit: Prepatellar Bursitis

As identified, the prepatellar bursa is the most frequently affected bursa in the knee. This bursa is strategically located on the front of the kneecap (patella), directly between the skin and the patella itself. Its superficial position makes it highly vulnerable to external forces.

Why it's so common:

• Direct Trauma: The prepatellar bursa is exposed to direct blows or falls onto the knee.
• Repetitive Pressure and Friction: Activities that involve prolonged kneeling, crawling, or repetitive rubbing against hard surfaces place significant stress on this bursa. This is why it's commonly known by occupational names such as "Housemaid's Knee," "Carpet Layer's Knee," or "Roofer's Knee." The constant pressure and friction can irritate the bursa, leading to inflammation and swelling.

When inflamed, the prepatellar bursa can swell significantly, forming a noticeable lump over the kneecap. This swelling is often accompanied by pain, tenderness, and sometimes warmth or redness, especially if an infection is present.

Other Common Knee Bursitides

While prepatellar bursitis takes the lead, several other knee bursae are also frequently affected, each with its own characteristic causes and symptoms.

• Pes Anserine Bursitis: Located on the inner side of the knee, about 2-3 inches below the joint line. This bursa lies beneath the tendons of three muscles: the sartorius, gracilis, and semitendinosus (collectively known as the "pes anserinus" or "goose's foot" due to their combined insertion).
  • Causes: Often results from overuse, tight hamstrings, obesity, valgus (knock-kneed) alignment, or degenerative arthritis of the knee. Common in runners, swimmers, and individuals with tight hamstrings.
• Infrapatellar Bursitis: There are two infrapatellar bursae:
  • Superficial Infrapatellar Bursa: Located between the skin and the patellar tendon, just below the kneecap. Similar to the prepatellar bursa, it can be irritated by direct trauma or prolonged kneeling ("Clergyman's Knee").
  • Deep Infrapatellar Bursa: Located between the patellar tendon and the tibia. Less common, often associated with direct trauma or overuse, particularly in activities involving repetitive jumping ("Jumper's Knee").
• Iliotibial Band (ITB) Bursitis: Located on the outer side of the knee, beneath the iliotibial band as it crosses the lateral femoral epicondyle.
  • Causes: Typically due to friction from the ITB rubbing over the bony prominence, often seen in runners, cyclists, and individuals with tight IT bands or biomechanical imbalances.

Causes and Risk Factors for Knee Bursitis

Beyond direct trauma and repetitive kneeling, several factors can contribute to the development of knee bursitis:

• Repetitive Motions and Overuse: Activities involving repeated bending, squatting, or jumping can irritate bursae.
• Direct Trauma: Falls or blows to the knee can cause acute inflammation.
• Prolonged Pressure: As seen with prepatellar bursitis, sustained pressure is a major factor.
• Infection (Septic Bursitis): A cut, scrape, or puncture wound over a bursa can allow bacteria to enter, leading to a painful, warm, red, and potentially fever-inducing infection.
• Underlying Medical Conditions: Certain systemic diseases, such as rheumatoid arthritis, gout, pseudogout, or diabetes, can increase the risk of bursitis.
• Improper Biomechanics: Muscle imbalances, poor running form, inadequate footwear, or structural issues (e.g., leg length discrepancy, flat feet) can alter forces around the knee, leading to increased stress on bursae.
• Obesity: Increased weight can place additional stress on knee joints and surrounding structures.

Recognizing the Symptoms

The symptoms of knee bursitis can vary in intensity but generally include:

• Pain: Localized pain that may worsen with movement of the knee or direct pressure on the affected bursa.
• Swelling: A visible lump or swelling over the affected area. This is often prominent in prepatellar bursitis.
• Tenderness: The area around the bursa feels tender to the touch.
• Redness and Warmth: Especially indicative of inflammation or, more concerningly, infection (septic bursitis).
• Limited Range of Motion: While often not severe, pain and swelling can restrict the knee's ability to fully bend or straighten.

Diagnosis and Treatment Approaches

Diagnosis typically involves a physical examination by a healthcare professional, assessing the location of pain, swelling, and range of motion. Imaging tests such as ultrasound or MRI may be used to confirm the diagnosis, rule out other conditions, or assess the extent of inflammation. If infection is suspected, fluid may be aspirated from the bursa for laboratory analysis.

Conservative Treatment (First-line approach):

• RICE Protocol: Rest the affected knee, Ice the area to reduce swelling, Compression with a bandage, and Elevation of the leg.
• NSAIDs: Over-the-counter non-steroidal anti-inflammatory drugs (e.g., ibuprofen, naproxen) to reduce pain and inflammation.
• Activity Modification: Avoiding activities that aggravate the bursa.
• Physical Therapy: Exercises to improve flexibility, strengthen surrounding muscles (quadriceps, hamstrings, glutes), correct biomechanical imbalances, and improve gait.
• Protective Padding: Using knee pads during activities that involve kneeling.

Medical Interventions:

• Corticosteroid Injections: For persistent non-infectious bursitis, an injection of corticosteroids into the bursa can rapidly reduce inflammation.
• Aspiration: Draining excess fluid from the bursa, especially if it's very large or painful. This also allows for fluid analysis.
• Antibiotics: If septic bursitis is diagnosed, a course of antibiotics is crucial to clear the infection.

Surgical Intervention:

• Bursectomy: In rare, chronic, or recurrent cases that don't respond to conservative treatment, surgical removal of the bursa (bursectomy) may be considered.

Prevention Strategies for Athletes and Enthusiasts

Preventing knee bursitis often involves a combination of modifying activities and optimizing body mechanics:

• Use Protective Padding: Always wear knee pads when engaging in activities that involve kneeling (e.g., gardening, construction work, floor laying).
• Proper Warm-up and Cool-down: Prepare your muscles and joints for activity and aid recovery.
• Gradual Progression: Avoid sudden increases in training intensity or duration. Allow your body to adapt.
• Strength and Flexibility Training: Focus on strengthening the muscles around the knee (quadriceps, hamstrings, glutes, calves) and maintaining flexibility, particularly in the hamstrings and IT band.
• Address Biomechanical Issues: Work with a physical therapist or coach to identify and correct gait abnormalities, muscle imbalances, or other biomechanical inefficiencies.
• Appropriate Footwear: Wear supportive shoes that are appropriate for your activity and replace them regularly.
• Maintain a Healthy Weight: Reducing excess body weight can lessen the load on your knee joints.

When to Seek Medical Attention

While many cases of knee bursitis resolve with conservative measures, it's important to seek medical attention if you experience:

• Severe pain or swelling that doesn't improve with rest and ice.
• Significant redness or warmth over the bursa.
• Fever or chills, which can indicate an infection (septic bursitis).
• Inability to move your knee or bear weight on your leg.
• Symptoms that persist despite home treatment.

Understanding the anatomy and common causes of knee bursitis, particularly prepatellar bursitis, empowers individuals to take proactive steps in prevention and seek timely, appropriate care when symptoms arise.