Knee pain can be the cause of much concern and confusion, especially if you have no idea what’s going on! To help give you a better understanding of pain and swelling in the knee, let’s explain a common condition affecting the area called: knee bursitis.
So what is bursitis exactly? Often, any swelling of the knee joint is called ‘water on the knee.’ However, there is a difference between fluid accumulation within a bursa specifically, and within the knee joint as a whole.
A bursa is a thin sac of synovial fluid (the body’s natural lubrication fluid) that is found between muscles, tendons, and skin, and allows these tissues to slide over one another without causing friction. These bursa are found throughout the body, particularly at interfaces where a lot is going on (think shoulders, hips, knees).
Unfortunately, bursa can sometimes become inflamed and irritated – a condition known as bursitis. As opposed to generalized knee joint swelling, there is a more localized swelling and tenderness with pressure applied in bursitis. Furthermore, as there are up to eleven bursa around the knee, depending on which one is inflamed the location and feeling of pain can vary.
Bursitis in the knee occurs mostly from overuse injuries and is less frequent due to trauma. The mechanism of injury influences which bursa is affected, with the most common ones being the: pre-patellar, infrapatellar, suprapatellar and pes anserinus bursa (anatomy fun fact: the ‘patella’ is the kneecap).
Prepatellar bursitis is common in those who kneel a lot (think gardener, roofer, carpet layer), and results in superficial swelling on the front of the knee.
Infrapatellar Bursitis often occurs in conjunction with ‘jumper’s knee’ (you guessed it, in jumping activities) from repetitive strain and irritation to the tendon just below the patella. This form can cause anterior knee pain that mimics a patellar tendinopathy and can be harder to treat.
Suprapatellar bursitis causes pain above the patella, under the quadriceps tendon; it is seen following an injury such as a fall to the knee or repetitive microtrauma – think running on soft/uneven surfaces or jobs that require crawling.