Your knee looks unusually round or puffy right over the kneecap. Maybe you spent the weekend gardening, working on flooring, or kneeling to fix something around the house. You can still walk, but putting your weight on that knee hurts.
One possible cause is prepatellar bursitis—sometimes called housemaid’s knee. This is swelling of a small fluid-filled cushion in front of the kneecap, not necessarily a problem inside the knee joint. Many cases improve without a procedure. The important exception is an infected bursa, which needs prompt medical attention.
What is prepatellar bursitis?
A bursa is a thin sac that helps soft tissues glide over nearby bone. The prepatellar bursa sits between the skin and the patella (kneecap). When repeated pressure or a direct blow irritates it, the sac can produce excess fluid and become visibly swollen.
Unlike the deeper swelling of a knee-joint effusion, prepatellar bursitis often creates a distinct, soft mound directly on the front of the kneecap. It may be tender when touched or when kneeling, while walking can remain relatively comfortable. The American Academy of Orthopaedic Surgeons (AAOS) describes repetitive kneeling, sports contact, and direct trauma as common triggers.
Why does kneeling make the front of my knee swell?
Repeated pressure rubs and compresses the bursa. People who garden, clean floors, install tile or carpet, work in trades, wrestle, or repeatedly kneel during exercise can develop irritation even without one memorable injury. A fall directly onto the kneecap can also trigger sudden swelling.
Gout, inflammatory arthritis, and a break in the skin can change the diagnosis and treatment. A small cut, scrape, or insect bite near the front of the knee may let bacteria enter the bursa. That can cause septic bursitis, which looks similar at first but is more serious.
Is this bursitis or a swollen knee joint?
The location of the swelling offers a clue, but it does not make the diagnosis by itself:
- Prepatellar bursitis: A rounded swelling sitting on top of the kneecap, often worse with direct pressure or kneeling.
- Knee-joint swelling: A more diffuse sense of fullness around the kneecap or in the whole joint. Arthritis, injury, bleeding, crystal disease, or joint infection may be involved.
- Other problems: A patella fracture after a fall, cellulitis of the skin, a tendon injury, or gout can sometimes resemble bursitis.
An orthopedic examination evaluates tenderness, the skin, strength, motion, and whether the knee can safely bear weight. Clinicians may use ultrasound to help locate a superficial fluid pocket or distinguish it from deeper joint swelling. X-rays may be needed after an injury or if a bone problem is suspected; an MRI is not routinely necessary for an otherwise typical case. Mayo Clinic explains the diagnostic options.
When is a swollen kneecap an urgent problem?
Arrange same-day medical assessment if the area is increasingly red, hot, or very tender; redness is spreading; there is drainage or a wound over the swelling; or you have fever or chills. Infection can occur even without a high fever. People with diabetes, immunosuppression, or a recent skin injury should have a lower threshold for evaluation.
Go to urgent or emergency care promptly for severe pain with inability to bear weight, inability to move the knee, a rapidly worsening hot and swollen joint, or feeling systemically ill. These symptoms may represent a joint infection, significant injury, or another condition that cannot safely be diagnosed from a photograph. An infected joint is particularly time-sensitive.
Do not try to puncture, squeeze, or drain a swollen kneecap at home. Needle puncture can introduce bacteria, and fluid may need laboratory testing. The AAOS guide and Cleveland Clinic patient resource both emphasize recognizing possible infection.
What helps noninfected prepatellar bursitis?
If an examination supports uncomplicated, noninfected bursitis, first-line treatment is usually nonsurgical:
- Remove the pressure. Pause kneeling and activities that keep irritating the front of the knee. If kneeling is unavoidable, use substantial knee padding and shorter work periods.
- Use cold packs. Apply ice through a towel for about 15–20 minutes at a time, several times per day as tolerated. Avoid placing ice directly on the skin.
- Consider gentle compression and elevation. A comfortable sleeve or wrap may help with swelling; it should not make the leg numb, cold, or more painful. Elevate the leg while resting.
- Use pain medicine only when appropriate. Acetaminophen or an anti-inflammatory medicine may help, depending on your medical history. NSAIDs are not suitable for everyone, including some people with kidney disease, ulcers, blood-thinner use, or other risks. Ask your clinician or pharmacist if unsure.
- Return gradually. Once symptoms settle, rebuild your normal activity without repeatedly provoking the bursa. Persistent difficulty with movement, balance, or strength may justify a tailored physical therapy plan.
There is no reliable fixed number of days to full recovery. Mild swelling may improve over days to weeks; ongoing kneeling can make symptoms persist or return. If the lump is growing, persists, or limits your work or daily life, it deserves evaluation rather than endless self-treatment.
Should the bursa be drained or injected?
Not every visible lump needs aspiration. Removing fluid with a needle may relieve a large, uncomfortable swelling or supply a diagnostic sample when infection, gout, or another cause is suspected. When infection is a concern, the fluid may be analyzed and cultured to guide treatment. The procedure has tradeoffs, including bleeding, recurrence, and a small risk of introducing infection.
A steroid injection is not routine treatment for every case. In selected persistent, clearly noninfected cases, a clinician may consider it after discussing benefits and risks such as skin changes, infection, or recurrence. A steroid should not be injected into a potentially infected bursa. The Mayo Clinic treatment overview outlines when aspiration or injection may be considered.
If the bursa is infected, treatment generally involves antibiotics, evaluation of whether fluid sampling or drainage is needed, and close follow-up. Patients with severe infection or significant medical risk may require hospital care. Repeatedly inflamed or persistently infected bursae sometimes require surgery, but bursectomy is uncommon. A systematic review of 702 patients across 10 studies found limited evidence for choosing among surgical approaches; the right treatment depends on the specific case.
Can physical therapy help prevent another episode?
Therapy does not simply “drain” an irritated bursa. But an individualized rehabilitation plan may help someone who has also developed knee stiffness, altered movement, weakness, or difficulty returning to work or sport. For recurring bursitis, pressure reduction and protection usually matter more than a complicated exercise program.
Knee pads, regular standing breaks, changes in kneeling technique, and prompt cleaning of any skin breaks can reduce repeated irritation. Someone with recurrent swelling should also be assessed for infection, gout, or another cause instead of assuming every flare is mechanical.
Common questions
Can I walk with prepatellar bursitis? Often yes, if walking is comfortable and there are no warning signs. Avoid kneeling or activities that increase pain. Trouble bearing weight warrants examination.
Is the fluid dangerous? Fluid from mechanical irritation may settle without intervention. Infection is the concern when warmth, redness, progressive tenderness, skin breaks, or systemic symptoms appear.
Do I need an MRI? Usually not for a typical superficial bursitis diagnosis. A clinician may use ultrasound or X-rays based on the examination and injury history. More advanced imaging is reserved for cases where it may change care.
Will draining it keep it from coming back? Not necessarily. Continued kneeling or other irritation can make fluid return; aspiration is not always the best first step.
Knee swelling care on Oʻahu and Hawaiʻi Island
Pacific Bone & Joint evaluates knee pain and injuries at its Honolulu, Waipahu/Kunia, Hilo, and Kona clinics. Depending on your symptoms, evaluation may include an examination, imaging, activity guidance, or coordination with physical therapy on Oʻahu. We help you distinguish simple superficial swelling from problems that need more urgent treatment.
If your kneecap stays swollen or the diagnosis is uncertain, request an orthopedic evaluation or call (808) 439-6201. Do not wait for a routine appointment if you have signs of infection or severe inability to use the knee.
This article offers general education and cannot diagnose an individual knee problem. Treatment, especially aspiration, antibiotics, or injections, requires a clinician’s evaluation.
