Knee Bursitis

Knee bursitis is inflammation of one of the bursae around the knee, most often from repeated kneeling, direct trauma, infection or crystal disease.

The clinically important bursae are the prepatellar bursa (housemaid's knee), the superficial and deep infrapatellar bursae (clergyman's knee), the pes anserine bursa on the medial proximal tibia, and the Baker cyst (popliteal cyst), which in adults is almost always secondary to intra-articular pathology.

The key decision in any superficial knee bursitis is septic or aseptic. Septic bursitis needs aspiration and antibiotics; aseptic bursitis is usually managed conservatively.

• •Prepatellar bursa: between the skin and the anterior patella. It does not communicate with the knee joint, which is why septic bursitis can occur without septic arthritis
• •Superficial infrapatellar bursa: between the skin and the tibial tubercle, vulnerable to kneeling
• •Deep infrapatellar bursa: between the patellar tendon and the anterior tibia, and may be irritated alongside patellar tendinopathy
• •Pes anserine bursa: between the conjoint tendons of sartorius, gracilis and semitendinosus and the medial tibial condyle, about 5 to 6 cm below the medial joint line
• •Baker cyst: in the posteromedial popliteal fossa, communicating with the joint through a one-way valve

Repetitive kneeling and direct trauma drive prepatellar and infrapatellar bursitis. Septic bursitis usually follows inoculation through a skin break, and Staphylococcus aureus causes 80 to 90% of cases, with streptococci most of the rest. Gout can affect the prepatellar bursa. Pes anserine pain syndrome typically accompanies medial compartment osteoarthritis (OA), obesity and pes planus.