Pes anserinus syndrome
Pes anserinus tendinopathy, pes anserinus bursitis

The pes anserinus is the insertion of three tendons on the medial side of the knee joint. Literally, pes anserinus means "goose foot", due to the shape of these three tendons. Pain in the pes anserinus may be caused by inflammation of one of the tendons or by bursitis. The pain is felt on the medial side of the knee.

Description of condition

The pes anserinus is formed by the tendons of three separate muscles: the gracilis, sartorius and semitendinosus. These tendons all attach to the tibia. The function of these three muscles is mainly to bend and rotate the knee, and to provide support in order to prevent valgus stress. Valgus stress is when the knee caves inward, which is why it is also referred to as being knock-kneed. The space between this combined tendon and the tibia contains a bursa. A bursa is a sac filled with fluid that ensures that the different structures slide over one another.

It is difficult to distinguish the difference between tendinitis (tendinopathy) and bursitis in pes anserinus. Hence, the term pes anserinus syndrome is used. The difference actually adds nothing because the treatment is the same in both cases.

Cause and history

An irritated, damaged or infected bursa or tendon causes symptoms. In this case, the bursa causes that the tendons cannot slide well with respect to the tibia.

Primarily the position of the knee (knock knee) causes symptoms in the pes anserinus. Because of the changed position, the tibia can exert more pressure on the bursa and tendons of the pes anserinus.

Additionally, tight hamstrings also cause symptoms in the pes anserinus. This is because one of the tendons, (the semitendinosus), is a tendon of one of the hamstrings.

In turn, tight hamstrings and the knock knee can have different causes. Besides the built of the body, wear and tear of the knee joint and meniscus problems constitute a risk of developing knock knee. Increased tension on the hamstrings may be caused by incorrect posture. The hamstrings are attached to the pelvis so that the position of the pelvis is decisive for the mobility of the hamstrings.

Risk factors for developing pes anserinus symptoms

• Female gender (the pelvis is usually wider, developing into knock knee faster).
  
• Obesity (the pressure on the knees becomes too high and this can cause knock knee).
  
• Osteoarthritis in the knee (which can cause knock knee).
  
• Diabetes (reduced circulation so that tendons and bursae recover less quickly).
  
• Rheumatism (reduced quality of the muscles results in higher likelihood of wear and tear).
  
• Repetitive sports (running, cycling, swimming can cause excessive strain).
  
• Flatfeet (which can play a role in the position of the knee).
  
• Local trauma (accident, fall or making a wrong movement).
  
• Osteophyte formation (extra ossification on the medial side of the knee).

Signs & symptoms

Typical symptoms include pain on the inside of the knee and pain when pressing where the tendons connect. The connection site is below the knee on the inside of the tibia. The pain often gets worse when walking up and down steps. The typical symptoms are not always present, and the location of the pain may be different in each case. Pain is often experienced over a larger area. As a result, it is difficult to distinguish whether the pain originates from the pes anserinus, medial meniscus or inner knee ligament.

The criteria defined for the diagnosis include:

• Pain on the inside of the knee.
  
• Pain when walking up and down steps.
  
• Pain in the morning.
  
• Morning stiffness at the location (of the pain) lasting at least one hour.
  
• Difficulty getting out of a chair or car.
  
• Local sensitivity.
  
• Local swelling.

Diagnosis

The diagnosis is made by a (general) physician or physiotherapist on the basis of asking some questions and a physical examination. The above-mentioned criteria play an important role in this. Additional examinations such as X-ray examination or ultrasound examination do not add anything for these symptoms.

An X-ray examination may, however, be used to determine the degree of osteoarthritis in the knee. Osteoarthritis is a risk factor for the development of pes anserinus symptoms.

An ultrasound examination identifies muscles, tendons and bursae, but it is known that this is not a reliable examination when it comes to pes anserinus symptoms.

When making the diagnosis, other problems in this region must be ruled out. Mainly meniscus problems and medial ligament damage cause pain in the same region. This should be taken into account when making the diagnosis.

Treatment

The treatment of pes anserinus syndrome focuses on reducing the inflammatory reaction. This may be achieved through (relative) rest, applying ice, and anti-inflammatory drugs prescribed by the (regular) physician. A local injection of anti-inflammatories may be administered. To sleep, placing a pillow between the knees is advised to reduce pressure on the painful spot.

In addition, the treatment consists of tackling the risk factors. If overweight, the patient is urgently advised to lose weight. If the patient has flat feet, these can be treated with insoles.

Physiotherapy plays an important role during treatment. The physiotherapist can treat the muscles around the knee joint through exercises and certain stretching techniques. Posture is worked on too, especially when the patient is knock-kneed. If necessary, strength training is recommended and given to prevent loss of muscle strength around the knee joint.

Exercises

You can check your symptoms using the online physiotherapy check or make an appointment with a physiotherapy practice in your locality.

References
Helfenstein, M. & Kuromoto, J. (2010). Anserine syndrome. Bras / Rheumatol. 2010;50(3):313-27.
Mohseni, M. & Graham, C. (2018). Bursitis, Pes Anserine. StatPearls Publishing; 2019 Jan.