Prepatellar bursitis is inflammation and fluid collection within the prepatellar bursa, located between the patella and the overlying subcutaneous tissue. It has been historically referred to as "housemaid's knee".
The main risk factors are compression such as repetitive kneeling and friction. However the clinician should keep in mind the possibility of an underlying rheumatological condition, especially rheumatoid arthritis and gout. Infection is another cause.
Anterior knee pain and swelling
Plain films may show soft tissue swelling and in chronic cases there may be clumps of calcifications.
On ultrasound there is hypoechoic fluid, and debris may be seen anterior to the patellar surface.
On MRI there is an oval shaped fluid-filled sac seen anterior to the patella. It shows up as low T1 and bright T2/fat sat signal intensity. With haemorrhage the T1 signal increases and the T2 GRE signal reduces. There may be an increased wall thickness.
Needle entry should only be done with caution due to the risk of infection and the associated morbidity with that.
Bursectomy is sometimes done in resistant cases.
- Deep infrapatellar bursitis | Radiology Reference Article | Radiopaedia.org