Conditions of the Knee Quiz

See Pre-patellar bursitis. Option C is correct. A bursa is a small fluid-filled sac that reduces friction where skin, tendon or muscle moves over bone. The pre-patellar bursa lies between the skin and the front of the patella (kneecap), and it lets the skin slide over the kneecap as the knee bends and straightens. Repeated minor trauma, such as prolonged kneeling, or a direct fall onto the knee irritates the bursa, so it becomes inflamed and fills with fluid. This produces a painful, red swelling directly over the front of the kneecap, which is why the condition is called housemaid's knee, after kneeling forwards to scrub a floor. The swelling sits outside the knee joint, so movement of the joint itself is usually not restricted. Rest, ice, elevation and over-the-counter painkillers are the usual first measures. If it fails to settle, the bursa may be aspirated and tested for infection, and antibiotics are given if infection is present.

• Structure: the pre-patellar bursa is a fluid-filled sac between the skin and the front of the patella.
• Cause: repeated kneeling or a direct fall inflames the bursa.
• Result: housemaid's knee, a painful, red swelling over the kneecap outside the joint.