Pes Anserine bursitis, Pes anserine syndrome, lower hamstring tendonitis

Ross Hauser, MD., Danielle R. Steilen-Matias, MMS, PA-C

We see many people with knee pain. More specifically we see many active people including runners with knee pain. They often have many diagnoses. Some are correct, some are not so correct. Sometimes they will display symptoms over their whole knee and not simply isolated to one area or another. However, some will have more obvious problems on one side of their knee than the other. Typically this will be more tender points on examination and obvious swelling. If these problems are on the inside of the knee towards the back of the leg, these problems may include Pes Anserine bursitis or Pes anserine syndrome.

Many people have pain seen in the inside bottom part of the knee. It can be caused by many problems beyond the Pes Anserine tendon. Typical of this and other knee pain is the pain increases with activity, swelling on the inner side of the knee may also worsen during activity.

Because there is no real telling what the knee problem is, knee MRIs will be ordered. While many patients are happy to get an MRI as they believe this will reveal what is causing their knee problem, as we will see in the research below, MRIs may confuse this knee pain problem and make the situation worse.

Discussion points of this article:

  • Pes anserine syndrome or Pes Anserine tendon injury: An opinion from doctors.
    • Patients with pes anserine syndrome may benefit from cortisone injections.
  • Poor accuracy of clinical diagnosis and MRI interpretation in pes anserine tendinitis bursitis syndrome
  • Pes anserine syndrome and knee osteoarthritis – a study on cortisone and physical therapy.
  • The knee is a whole joint organ made up of individual parts that make up the whole, Pes Anserine bursitis may only be one knee problem among many.

An introduction to the basic mechanisms of pes anserinus tendinopathy

The pes anserinus tendon, also known as the inside hamstring muscles, flexes the knee and stabilizes the inside of the knee. Most of us have very, very, very weak hamstring muscles that are very short because we sit for a large portion of our day. Many patients, especially those with fallen arches are prone to strains in these muscles. The tibia tends to rotate outward to compensate for the fallen arch. This outward rotation of the tibia places additional stress on the pes anserinus tendons. Eventually, these tendons become lax and are no longer able to control the tibial movement, adding to the chronic knee pain. Arch support may be prescribed to reestablish the arch. Pes anserine tendonitis is one of the most frequent types of knee tendonitis.

Whenever there is knee pain there are treatment options, some work, some don’t.

Whenever there is knee pain there are treatment options, some work, some don’t. The person who self-manages their knee pain will try to stay active with Non-steroidal anti-inflammatory drugs (NSAIDs) for the pain and swelling. Ice and cold packs will become part of their regular day.

Eventually, a visit to the general practitioner will result in a referral to a knee specialist, and then more potent oral medications will be offered. If the swelling in the pes anserine area is more severe, then cortisone injections may be recommended. Down the line, physical therapy may be prescribed and along the way knee braces, tapes, shoe inserts, and other remedies will be tried.

It is likely that you are reading this article because your knee has not gotten better on its own and because you like to be active you have tried to manage through it. In fact, you may have felt better resuming Your sport or exercise program only to have the pain return and be a little more intense the next time it does. You are getting to the point where you need to find alternatives to your chronic knee pain.

In the image below we see the Semitendinosus tendon, gracilis tendon, and the subartorial or pes anserine bursa

In the image we see the Semitendinosus tendon, gracilis tendon, and the subartorial or pes anserine bursa 

Pes anserine syndrome or Pes Anserine tendon injury: An opinion from doctors

An opinion from doctors at the University of Florida, Orthopaedics and Sports Medicine Institute offers us a good introduction to the challenges of Pes anserine syndrome or Pes Anserine tendon injury resulting in chronic knee pain. Here are the summary highlights of this opinion. (1)

  • Pes anserine syndrome is usually diagnosed with the predominant finding of pain inside and behind the shin approximately 2 to 3 inches below the knee.
  • The source of the patient’s pain is difficult to identify (as we will discuss below, it can often be misdiagnosed) but may include either the pes anserine itself (comprised of the sartorius, gracilis, and semitendinosus muscle tendons) and/or the associated pes anserine bursa.
  • There is an association between pes anserine syndrome and knee osteoarthritis, with 20% to 46% of patients with symptomatic knee arthritis also having pes anserine syndrome.

Patients with pes anserine syndrome may benefit from cortisone injections.

  • Patients with pes anserine syndrome may benefit from cortisone injections. However, not all symptomatic patients may benefit. In cases where both conditions are present (pes anserine syndrome and knee osteoarthritis) but only an intra-articular injection (into the knee joint not around the knee joint) was performed, we have noted that patients will often return to the clinic stating that “the intra-articular injection did not work” and that they are limited in participation of their physical therapy by their continued pain. It would be more beneficial to inject into the knee and around the knee with cortisone.

Pes anserine syndrome and knee osteoarthritis – a study on cortisone and physical therapy.

A July 2016 study in the Journal of Physical Therapy Science (2) looked at patients with just knee osteoarthritis and those with knee osteoarthritis and pes anserine tendino-bursitis. They wanted to compare the patient’s knee function ability in both cases.

Next, they wanted to compare treatments, specifically physical therapy and corticosteroid injection for patients with pes anserine tendino-bursitis.

Sixty patients with knee osteoarthritis and pes anserine tendino-bursitis (Group 1) and 57 patients with knee osteoarthritis but without pes anserine tendino-bursitis (Group 2) were enrolled in the study.

The pes anserine tendino-bursitis group was randomly divided into two groups (Groups A and B). Physical therapy (PT) modalities were applied to the first group (Group A), and the second group (Group B) received corticosteroid injections to the pes anserine area.

Eight weeks later, patients’ pain scores were assessed.  Both treatments, Physical therapy, and corticosteroid injections resulted in significant improvements in pain and function scores, but no significant difference was detected between the [physical therapy and corticosteroid injection groups.

Findings: “Patients with pes anserine tendino-bursitis tend to have more severe pain, more altered functionality, and greater disability than those with knee osteoarthritis alone. Both corticosteroid injection and physical therapy are effective methods of treatment for pes anserine tendino-bursitis. Injection therapy can be considered an effective, inexpensive, and fast therapeutic method.

  • Adverse joint events after intra-articular corticosteroid injection, including accelerated osteoarthritis progression, subchondral insufficiency fracture, complications of osteonecrosis, and rapid joint destruction with bone loss, are becoming more recognized by physicians, including radiologists, who may consider adding these risks to the patient consent. (3)

The knee is a whole joint organ made up of individual parts that make up the whole

In this section, we want to stress the concept that knee problems, especially chronic knee problems are not as simple to understand as a single-component diagnosis, such as Pes Anserine bursitis or Pes anserine syndrome. Knee problems are more probably a problem of many conditions.

The knee has four major bursa. The suprapatellar, infrapatellar, pes anserine, and prepatellar. Typically knee injuries do not occur in isolation, meaning that if you injure a ligament or tendon, it is likely done with enough force or impact to cause lesser injuries to other structures.

This is pointed out by a June 2021 study (4) assessing co-injuries in patients who suffered a medial collateral ligament. In this study, the researchers found:

  • Isolated MCL lesion of 3%. This points to the rarity of injuring your MCL alone.
  • Associated injuries were:
    • medial meniscus injury (46.15%),
    • anterior cruciate ligament injury (30.7%),
    • isolated bone contusion (18.46%),
    • chondral (cartilage damage) injuries (37.58%),
    • medial vastus injury – quadriceps muscle (14.51%),
    • patellar medial retinacular injury (14.51%),
    • vastus lateral injury – quadriceps muscle  (9.23%),
    • posterior cruciate ligament injury (6.15%),
    • lateral meniscus injury (4.61%),
    • iliotibial band tenosynovitis (4.61%),
    • medial facet avulsion fracture (3.07%),
    • Pes Anserine tenosynovitis (3.07%).

As you would imagine, the co-existence of this large group of co-conditions would make any diagnosis of Pes Anserine bursitis difficult to imagine as being an isolated problem.

This is also seen in the information provided to us by people looking for patient services. Often people will tell us their desire to remain active in sports, but of their current knee challenges which are the result of a long medical history.

Typically people will contact us and tell us about a Primary ACL Reconstruction, then an ACL Reconstruction Revision, and Medial Meniscus Repair. Then another meniscus surgery. They will also tell us of a subsequent injury that damaged their pes anserine.

Poor accuracy of clinical diagnosis and MRI interpretation in pes anserine tendinitis bursitis syndrome

In May 2021, doctors wrote (5) about the “poor accuracy of clinical diagnosis in pes anserine tendinitis bursitis syndrome.” What the doctors were questioning was the accuracy of clinical diagnosis as compared to MRI findings.

Typically MRI findings can be questioned for accuracy for a lower knee injury. Here the doctors compared these MRI findings to a doctor’s clinical ability to determine a pes anserine. What these researchers found was “that clinical pes anserine tendinitis bursitis syndrome diagnoses may be inaccurate, particularly in the presence of such invasive therapies as an injection, and that diagnoses based on imaging methods would be more accurate.”

The invasive injection would be cortisone or painkiller to determine if the cause of the knee pain was found.

In the US National Library of Medicine’s STATPEARLS (6) Updated January 2024, Mayo Clinic authors write: “Generally speaking, imaging does not assist with the diagnosis of pes anserine bursitis. However, plain knee radiographs (x-rays) are usually obtained to observe for any underlying bony abnormalities, including osteoarthritis. Ultrasonography may be used as an adjunct to evaluate other causes of localized swelling, including joint effusions. Though rarely indicated in an urgent setting, magnetic resonance imaging (MRI) may help assess for knee pathology and rule out alternative diagnoses.”

Pes Anserine bursitis may cause bone overgrowth within the thigh bone that may be misdiagnosed as a bone tumor.

Doctors at the Cleveland Clinic wrote a paper in November 2019 in the journal Skeletal Radiology (7) about the challenges an MRI may present in the accuracy of diagnosis. Here in this paper, they warn that bone changes such as the development of bone within the thigh be misinterpreted as bone cancer. “Pes anserine bursitis with intramedullary extension (bone extension inside the thigh bone) is an unusual presentation of bursitis that may simulate a neoplasm clinically and radiologically (the appearance of a bone tumor). To avoid misdiagnosis, radiologists should be aware of the occurrence of osseous changes in the tibia confluent with pes anserine bursitis.

MRI’s then too would not be considered useful in non-acute settings.

While Pes anserine syndrome is typically a problem of more active people, it can also be seen in people who had a previous knee replacement. This was demonstrated in a case history presented in the Journal of Clinical Orthopaedics and Trauma (8) in February 2020:

Pes anserine syndrome occurs in patients with diabetes mellitus, osteoarthritis, rheumatoid arthritis, and in overweight patients. It is a challenge to identify the causes of knee pain following knee replacement surgery.

“(The authors) present a case report of pes anserine syndrome in a 79-year-old female who had undergone knee arthroplasty 13 years prior. She was pain-free until one year ago when her knee pain resurfaced without any symptoms of infection or history of trauma. She was successfully treated with a combination of stretching exercises and steroidal local steroid injection. We want to highlight that such common condition as pes anserine syndrome, could occur in total knee arthroplasty, and should be considered as one of the possible diagnoses.”

Overreliance of MRI

A November 2022 case history presented in the journal Cureus (14) tells the story of a  57-year-old obese woman who showed up at an emergency room with an eight-week history of right knee pain following an injury. Soon after the injury, she made an appointment with her general practitioner. “The GP took a history of the mechanism of injury and a description of the pain; however, no physical examination was performed at this time. She was booked for a knee MRI; no X-ray was requested since ligament injuries were suspected. The scan reported mild osteoarthritic changes within the knee, which may have contributed to her ongoing symptoms; however, no obvious cause was identified for the acute exacerbation of knee pain. She was then advised to rest and allow the knee to get better with time.”

At eight weeks, she came to the emergency room reporting that her knee pain had neither improved nor worsened in severity despite this period of rest. On examination, she was in poorer health and overweight with a noticeable limp.  . . On examination, she was diagnosed clinically with pes anserinus bursitis and sent to physical therapy.  The therapy protocol focused on strengthening and lengthening the muscles of the leg, with a particular focus on quadricep, hamstring, and groin exercises. . . At follow-up, she reported an improvement in her symptoms, with a reduced limp and improved strength throughout, and attributed this to good compliance with rehabilitation exercises.

What the researchers wanted to stress in this case history was the overreliance on MRI and imaging: “Pes anserinus bursitis is frequently misdiagnosed and often not considered a differential diagnosis for a painful knee. This case has highlighted the importance of performing a thorough history and clinical examination when considering the challenge of diagnosing musculoskeletal knee pain, particularly in primary care.

This case has also demonstrated the dangers of overreliance on imaging modalities. In particular, referring patients for imaging too early may lead to a loss of patient confidence and worse patient outcomes, as some musculoskeletal problems do not improve with time alone. “

Medical Treatment options

Extracorporeal shockwave therapy (ESWT) Pes Anserine

A June 2017 study in the journal Advanced Biomedical Research (9) investigated the effect of Extracorporeal shockwave therapy (ESWT) on pes anserine bursitis.

The patients in this study suffered from pes anserine bursitis for at least three months. They also had not responded to the traditional conservative methods mentioned already in this article. In total, the 40 patients of this study were divided into two 20-member experimental groups (extracorporeal shock wave therapy [ESWT] and sham ESWT).

Results: In the ESWT group, the average patient pain score as assessed by standard scoring systems was significantly lower than in the sham ESWT group immediately after intervention (3rd week) and 8 weeks after the end of treatment. The results showed that ESWT could be effective in reducing the pain and treating pes anserine bursitis.

Most Extracorporeal shockwave therapy research does not include Pes Anserine tendinopathy

Platelet Rich Plasma injections for Pes anserinus pain syndrome

A 2014 paper (10) from the Department of Orthopaedics, Military Institute of Medicine, Warsaw, Poland examined the effect of Platket Rich Plasma for Pes anserinus pain syndrome. They targeted a group of women over the age of 50. Here is what they wrote:

  • Pes anserinus pain syndrome is a relatively common condition in overweight and obese women over 50 years of age.
  • This study demonstrated that greater intensity of degenerative changes of the knee joint was accompanied by more severe pain in the pes anserinus area.
  • Platelet-rich plasma is an effective treatment for pes anserinus pain. It produces pain relief and thus significantly improves the quality of life.
  • The response to platelet-derived growth factors was poorer in advanced degenerative knee joint disease.

I personally remember coming across a classic pes anserinus case while on rounds as a new hospital doctor. A 35-year-old nurse told me her rheumatologist diagnosed her with arthritis and had prescribed anti-inflammatory medication. When he examined her knee, he found that she had a full range of motion.

The full range of motion of the knee makes it unlikely arthritis is the cause of knee pain. On further examination, I was able to elicit a positive “jump-off-her-chair sign” when I pressed my thumb into the pes anserinus area showing pes anserinus tendonitis.

When I used to give lectures and presentations, I would often ask the audience, “What is the number one reason for severe knee pain in the elderly?” The overwhelming response is arthritis. In many people we see, the number one reason for severe knee pain in the elderly is pes anserinus tendonitis which, when left untreated, may contribute to developing arthritis. Even in cases of significant arthritis, crippling knee pain is most often due to pes anserinus tendonitis or bursitis.

A June 2021 study in the journal Transfusion and Apheresis Science (13) published outcomes on the effectiveness and safety of ultrasound-guided leukocyte-rich platelet-rich plasma  injection in sixty patients with pes anserinus tendinobursitis. The 60 patients were split into two groups, one group receiving one injection, and the other group receiving two injections a week apart.

Both groups showed significant improvement in all pain, disability, and function scores at the 4th and 12th weeks after treatment. When the two groups were compared with each other, there was no statistical difference.

When all patients were evaluated with Likert scale (the patient’s opinion on how the treatment worked for them), in the 12th week after treatment, the patients noted:

  • complete healing in 22 (36.7 %) patients,
  • significant relief in 25 (41.7 %) patients,
  • mild relief in 4 (6.7 %) patients,
  • 5 (8.3 %) same as before treatment patients,
  • and worsened pain in 4 (6.7 %) patients were seen.

Prolotherapy versus local corticosteroid soft tissue injection for the treatment of chronic anserine bursitis

An April 2024 study in the American Journal of Physical Medicine & Rehabilitation (12) compared the effectiveness of corticosteroids, oxygen-ozone (O2-O3), and dextrose 20% prolotherapy for pes anserine bursitis.  There were 72 patients in this study who were randomly assigned among the three treatment groups. Outcome measures included pain severity using the visual analog scale (VAS) and the Western Ontario McMaster University osteoarthritis index (WOMAC) that was evaluated before the intervention, one and eight weeks after that.

  • Statistically significant improvement in pain severity and function was in favor of corticosteroids and oxygen-ozone (O2-O3) after one week and in favor of oxygen-ozone (O2-O3) and prolotherapy groups after eight weeks.

Conclusion: All three treatment options are effective for patients with pes anserine bursitis. “This study showed that the effects of O2-O3 injection and prolotherapy last longer than those of corticosteroid injection.”

What are these injections?

Prolotherapy is a nonsurgical regenerative injection technique that introduces small amounts of dextrose to the site of painful and degenerated tendon insertions (entheses). It is injected at the tendon attachment site to the bone.

  • Prolotherapy is an in-office injection treatment that research and medical studies have shown to be an effective, trustworthy, and reliable alternative to surgical and ineffective conservative care treatments.

Lyftogt Perineural Injection Treatment™ (also called Neurofascial Prolotherapy, as well as Neural Prolotherapy and Subcutaneous Prolotherapy) is an injection treatment sometimes used as a side-by-side treatment with traditional dextrose-based Prolotherapy. As these techniques work on different aspects of knee pain, in combination they can diminish the patient’s pain

In Dextrose base Prolotherapy the ligament and tendon attachments are being treated, in Perineural Injection, the nerves are being treated.

Prolotherapy injections along the arch of the foot will also prove beneficial. Prolotherapy injections into the pes anserinus attachments to the bone strengthen the tendon attachments and can resolve chronic knee pain.

A January 2022 paper in the Ain-Shams Journal of Anesthesiology (11) examined the effectiveness of Neural prolotherapy versus local corticosteroid injection for pain relief and improvement of function in patients with chronic anserine bursitis.

The enrolled patients were randomly assigned to receive neural prolotherapy (subcutaneous perineural injection of dextrose 5% solution) (neural prolotherapy group) or a single local soft tissue injection of corticosteroid (corticosteroid group).

Outcome measures included standard pain and function outcomes and overall anserine bursitis pain severity using the visual analog scale (0-10 pain scale) and clinically assessed the presence of tenderness on the anserine bursa region. Patients were evaluated before injection and after intervention by 4 weeks.

Please see our article Tendinitis and Tendinosis Treatments – Injections for Chronic Tendinopathy for more information on different injections


Pes anserine tendonitis is one of the most frequent types of knee tendonitis. The tendinosis of this structure is characterized by inflammation of the inside knee and often coexists with other knee disorders. Chronic stress from activity or contusion to the pes anserine bursa near the tibial insertion may precipitate the inflammation. An underlying ligament injury is often a coexisting problem, causing joint instability and potentially irritating the tendon as it comes in contact with the structures of the unstable knee. As with other tendinopathies, pes anserine tendonitis can be treated with Prolotherapy. Positive results have been obtained, resulting in a stabilized knee joint.

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