Knee bursitis and Baker’s cyst
Why is there swelling at the front or back of my knee?
Swelling of a bursa in front of the kneecap, or a fluid-filled cyst behind the knee. Treatment targets the cause.
What it feels like
Prepatellar bursitis: a soft swelling in front of the kneecap, often after kneeling a lot. Baker’s cyst: a swelling or tightness at the back of the knee, more noticeable when the knee is straight, sometimes with stiffness bending it.
What is actually happening
Bursae are small fluid-filled sacs that reduce friction. The bursa in front of the kneecap can fill with fluid from repeated kneeling or a knock, and occasionally becomes infected. A Baker’s cyst is a pocket of joint fluid at the back of the knee, usually linked to another knee problem such as osteoarthritis or a meniscus tear, which is producing extra fluid.
When to see a doctor urgently
See a doctor the same day if a swelling at the front of the knee is red, hot and painful, or you have a fever. See a doctor urgently if you develop calf pain, swelling, warmth or redness, as this can be a ruptured Baker’s cyst or a blood clot, and a blood clot needs to be ruled out.
How it is assessed
Assessment includes the location and history of the swelling, signs of infection, knee range of motion and strength, and assessment of the knee joint for the underlying problem that often drives a Baker’s cyst.
How it is treated
A systematic review of prepatellar bursitis found that non-infected bursitis is usually managed conservatively with protection from kneeling and pressure, while infected bursitis needs medical treatment. A systematic review of popliteal (Baker’s) cysts found that treatment works best when it addresses the underlying knee condition. Physiotherapy focuses on that underlying problem, for example strengthening for knee osteoarthritis or meniscus rehabilitation, alongside activity changes.
What to do first
Avoid kneeling or use thick knee pads, keep the knee moving within comfort, and have it assessed so that the underlying cause is identified.
Where this is assessed
- The Runner's Academy St. Clair West · Mon/Wed/Fri · 3:00 PM – 6:30 PM Book at Runner's Academy
- Athlete's Care Sports Medicine Centres Yonge & Eglinton · Mon/Wed/Fri · 8:00 AM – 2:00 PM Book at Athlete's Care
- Push Pounds Sports Medicine Downtown Toronto · Tue/Thu · 8:30 AM – 6:30 PM Call Push Pounds to book
References
This page is based on the following clinical practice guidelines and research.
- Brown OS, Smith TO, Parsons T, et al. Management of septic and aseptic prepatellar bursitis: a systematic review. Arch Orthop Trauma Surg. 2022;142(10):2445-2457.
- Van Nest DS, Tjoumakaris FP, Smith BJ, et al. Popliteal Cysts: A Systematic Review of Nonoperative and Operative Treatment. JBJS Rev. 2020;8(3):e0139.