Knee bursitis

When irritated bursae can become swollen and very painful, a condition known as bursitis. Because bursitis is most often a result of excessive loading on the knee, it often coexists with tendinopathy. Over time, excessive loading of the knee may lead to osteo-arthritis.

Although the knee has around a dozen bursae, only four are commonly a source of pain.   

• Pes anserinus bursitis is very common and is associated with pain in the front of the knee that is  deep, sharp and “bone” like. This bursa is located between the upper inner side of the leg bone and the pes anserinus, which is a tendon shared by three large thigh muscles. These muscles include a front thigh muscle (sartorius), which is in fact the longest muscle in your body, an inner thigh muscle (gracilis) and a back thigh or hamstring muscle (semitendinosis). Excessive pull on the tendon by one or more of these muscles is the most common cause of pes anserinus bursitis.

• Popliteal bursitis, also known as Baker’s cyst and popliteal cyst, is associated with a relatively large painful mass behind the knee. The cyst may extend down into the leg or up into the back of the thigh. The popliteal bursa is located between the upper end of the calf muscle (gastrocnemius), the lower end of a hamstring muscle (semimembranosis) and the underlying thigh bone close to the inner (medial) side of the knee joint. Excessive loading from one or both of these muscles is the most common cause of popliteal bursitis. In around 40% of people with this condition it is an expansion of the inner lining of the knee joint so swelling of the knee joint, such as may occur with arthritis, can also lead to pain and swelling of the popliteal bursa.       

• Iliotibial bursitis, is a common source of pain at the outer side of the knee. The iliotibial bursa is located between the lower end of an outer thigh tendon (iliotibial band) and the outer leg bone close to the knee joint. Iliotibial bursitis, is usually due to excessive pressure from the iliotibial band. 

• Infrapatella bursitis is associated with pain below immediately below the kneecap. The infrapatella bursa is located between the patella ligament, which attaches the lower end of the kneecap to the leg bone, and the leg bone (tibia). It often co-exists with “jumpers knee”.

Two other less common types of knee bursitis are:

• Prepatella bursitis is associated with pain felt at the front of the kneecap. The prepatella bursae overlies the front of the kneecap. It  affects those who are required to work on their knees for extended periods of time such plumbers, electricians, carpet layers and gardeners.

• Suprapatella bursitis is associated with pain immediately above the kneecap. The suprapatella bursa extends from underneath the kneecap and the muscles at the front of the thigh (the quadriceps muscles). Suprapatella bursitis is most often the result of excessive repetitive pressure being placed on it by the quadriceps muscle.