Knee bursitis is a condition where a small, fluid-filled sac, called a bursa, near the knee joint becomes inflamed. This inflammation causes the bursa to produce excessive fluid, leading to visible and palpable changes around the knee. The appearance of bursitis is distinct because the swelling is localized outside of the main knee joint capsule.
The Basic Appearance and Feel
The most common visual sign of knee bursitis is localized swelling, which often appears abruptly as a distinct lump or bulge over the affected area. The fluid-filled sac typically feels soft and somewhat squishy, often described as having a “boggy” or “fluctuant” texture when pressed lightly.
The skin overlying the inflamed bursa commonly shows signs of inflammation, including increased warmth and redness or a pinkish-purple discoloration. This warmth is a result of increased blood flow to the area as the body attempts to resolve the irritation.
Tenderness is characteristic of the condition, meaning the area is painful when touched or pressured. While swelling is noticeable, pain levels vary, sometimes only occurring during specific movements like kneeling or bending the knee.
Identifying the Specific Location
The precise location of the swelling is the most telling feature, as it differentiates the types of knee bursitis. The knee has several bursae, but the visual manifestation typically involves one of three major sites. Each site correlates to a specific bursa that swells due to friction or trauma in that particular area.
Prepatellar Bursitis (Housemaid’s Knee)
This is one of the most common forms, characterized by swelling directly over the kneecap (patella). The fluid collection is superficial, sitting just beneath the skin, causing the kneecap to look noticeably puffy and rounded. Because of its position, the visible lump is centered on the front of the knee. This presentation is often associated with prolonged kneeling, giving it the common name “Housemaid’s Knee.”
Infrapatellar Bursitis (Clergyman’s Knee)
Infrapatellar bursitis causes swelling in the area just below the kneecap, over the patellar tendon. The visible bulge is located near the top of the shinbone (tibia), rather than directly on the kneecap. Symptoms here can sometimes be mistaken for patellar tendinitis, but bursitis is identified by the distinct, localized fluid collection.
Pes Anserine Bursitis
This type of bursitis causes visible or palpable swelling on the inner side of the knee. The swelling is located approximately two to three inches (five to seven centimeters) below the joint line, on the upper part of the shinbone. Unlike the other types, the swelling here is often less prominent visually but is marked by tenderness directly over the insertion point of the hamstring tendons.
Acute vs. Chronic Presentation
The speed of onset and duration significantly affect the visual characteristics of the bursa. Acute bursitis occurs rapidly, often due to sudden impact or trauma. The swelling develops quickly and is typically accompanied by greater redness and warmth than chronic forms.
When acute bursitis is infected (septic bursitis), the visual signs are more pronounced. The area becomes extremely red, often with a deep coloration, and is intensely hot to the touch. The fluid sac may also feel taut or very firm due to increased pressure and inflammatory response.
Chronic bursitis develops gradually from repeated irritation or overuse. The visible swelling may be persistent but less dramatically red or warm than an acute flare-up. Over time, the bursa walls can thicken, causing the lump to feel more firm, rubbery, or nodular, rather than purely soft.
When to Seek Medical Attention
While many cases of knee bursitis improve with rest and basic care, certain visual and systemic cues indicate a need for professional medical evaluation. The most urgent signs suggest an infection.
These signs include:
- A rapidly worsening increase in redness and warmth over the bursa, especially if the skin feels extremely hot.
- A high fever or the presence of chills alongside the knee symptoms.
- Streaks of redness spreading away from the swollen area, which can indicate the infection is spreading.
- Severe, debilitating pain, or an inability to move the knee joint, even slightly.