Many individuals suffer from debilitating knee pain at some point during their life. An uncommon cause of medial knee pain is injury to the pes anserine bursa. Pes anserine was named for the structure’s similarity in appearance to the webbed foot of a goose. Translated from Latin, “pes” means “foot,” and “anserine” means “goose.” Pes anserine pathology, often overlooked in the differential diagnosis of medial knee pain, can result from direct trauma, overuse, or as part of the secondary symptoms of another disease process.
It is difficult to determine the frequency of pes anserine bursitis due to the considerable overlap with other knee conditions. The prevalence has been reported as low as 0.33% in a study of 10,000 individuals while another study that drew on data from the 2010 Population National Census of Mexico found it was the most common of the lower limb syndromes and pes anserine pain (not necessarily bursitis) with associated osteoarthritis was present in more than 90% of cases.
A smaller study of magnetic resonance imaging from 24 patients aged 30 to 50 years found 2.5% of adults with medial or posteromedial joint pain had pes anserine bursitis.
Pes anserine bursitis may also be a secondary diagnosis as it has been associated with being overweight and the presence of osteoarthritis. One series of radiographic images found knee osteoarthritis in 93% of patients with diagnosed pes anserine bursitis. There seems to be a relationship between diabetes and this condition, too.
In 96 patients with non-insulin dependent diabetes, 34% had pes anserine bursitis while there were no cases in the non-diabetic control group. An additional study also found a prevalence of nearly 30% of 48 patients with type 2 diabetes. Among them, osteoarthritis and diabetes would be the primary diagnosis, as pes anserine bursitis occurs secondary to the other conditions.
Pes anserine bursa anatomy
Knee joint stability can be compromised by anatomical anomalies, arthritic changes, overuse injury, or trauma. The knee is stable in extension due to the bony junction provided by the screw-home mechanism.
When the knee is unlocked, it relies on soft tissue structures to provide its stability. The anterior and posterior cruciate ligaments primarily resist translation of the tibia on the femur. The secondary function of both ligaments is to resist rotational forces at the knee. The medial and lateral collateral ligaments resist valgus and varus stress, respectively and also assist in resisting rotation.
There are two menisci wedged between the tibia and fibula. The medial meniscus is “C” shaped while the lateral meniscus more closely resembles an “O.” The larger medial meniscus is prone to injury due to its shape. The purpose of the menisci is to disperse axial loads to spare the articular cartilage on the bony surfaces of the tibia and fibula. The medial meniscus is firmly attached to the medial joint capsule and thus moves less during joint motion than it’s lateral counterpart.
Pes anserine also affords the knee some of it’s medial stability. Pes anserine is formed by the conjoined tendons of the gracilis, sartorius, and semitendinosus muscles as they form a broad structure that covers the medial aspect of the knee. The pes anserine bursa, one of 13 bursae around the knee joint, is located between the tibia and the tendinous attachments approximately five centimeters below the medial joint line.
During knee motion, the pes anserine bursa is stressed during active flexion and adduction as the hamstring and adductor muscles contract and compress the bursa between the soft tissues and the bone. When pes anserine bursitis is present, the patient experiences pain with repeated knee flexion and extension (such as with stair climbing).
There also seems to be a relationship between pes anserine and overweight women. Women tend to have a wider pelvis which leads to a larger Q-angle. Larger Q-angles can be associated with tight adductors (and weak abductors) which could provide an anatomical explanation for pain and compression to the pes anserine bursa in these individuals.
Pes anserine bursitis causes
Bursitis is a general term used to describe irritation of any bursae. Bursae are hollow structures found throughout the body in areas of increased friction between soft tissue and bony structures. Inflammation of the pes anserine bursa is caused by excessive friction to the bursa from valgus or rotatory stress, degenerative joint disease (osteoarthritis), or direct trauma to the area.
Similar to other conditions in the knee, pes anserine bursitis may be associated with mechanical derangement, trauma, obesity, and overuse. Medial compartment osteoarthritis is frequently present in patients with this condition. Running, basketball, and racquet sports may contribute to the development of pes anserine bursitis also.
This condition is common in overweight, middle-aged women where treatments for knee joint pathology have been unsuccessful. Oftentimes, these women present to orthopedists with knee arthritis or meniscus tears but careful examination reveals medial knee tenderness at the pes anserine bursa rather than the medial joint line. Correctly identifying the pes anserine bursa as the source of pain may avoid unnecessary surgical procedures based on incidental findings on imaging studies.
Irritation to the medial knee region may also be caused dysfunction stemming from the soft tissue and bony structures supporting the knee. Conditions that cause persistent knee flexion such as a hamstring strain or calf strain could result in irritation to the bursa.
An altered gait pattern caused by an attempt at pain-avoidance in patellofemoral pain syndrome could create lasting knee flexion as well. In repetitive activities such as walking, this flexed position can become problematic as it alters the wear patterns of the joint surfaces and does not allow the normal metabolic processes that are integral to soft tissue health to occur. In these cases, restoring full knee extension range of motion may be an easy and effective management strategy.
Medial knee pain may also be caused by internal derangement of the knee. If the internal derangement causes mechanical symptoms (decreased range of motion, locking, etc.), inflammation of the bursa and other soft tissue structures of the knee may result from these abnormal forces.
All that said, the diagnosis of pes anserine is not without controversy. Historically, MRI studies that showed the presence of fluid within the pes anserine bursa in patients with medial menisectomy lent to the validity of bursal involvement.
Conversely, Uson et al. examined ultrasounds of 37 patients with diagnosed pes anserine bursitis revealed that bursal enlargement was only present in two patients.
More recently, Unlu et al. studied 48 patients with type 2 diabetes and clinically diagnosed pes anserine bursitis found that less than 10% had ultrasonographic evidence of bursal swelling or pes anserine tendinopathy. Participants in this study with pes anserine bursitis or tendinitis had medial meniscopathy, osteoarthritis, popliteal cysts, and suprapatellar recess effusions more often than participants in the control group. It is possible that the pes anserine bursa is incorrectly identified as the faulty structure in these cases but a more plausible explanation for this pain has yet to be presented.
Pes anserine bursitis diagnosis
The best exam findings to confirm the presence of bursitis are tenderness to palpation, and pain with active motion (the contracting muscle compresses the bursa between the muscle and the bone) and passive motion (the lengthened muscle compresses the bursa between the muscle and the bone).
The subjective symptom presentation often includes pain at the medial aspect of the knee that worsens when rising from a seated position, climbing stairs, or sitting cross-legged (any flexion of the knee or lengthening of the adductors reproduces pain).
Gracilis. sartorius, and semitendinosus act in concert to flex the knee and resist tibial rotation when crossing one leg over the other and, as such, this position can be a useful diagnostic exam where reproduction of pain is a positive sign. Also, these patients often report weakness, stiffness, and decreased range of motion around their knees. Point tenderness is a cardinal sign of bursitis while inflammation may or may not be present. Patients with an established diagnosis of osteoarthritis of the knee should be carefully screened for pes anserine pain and bursitis.
The classic objective symptoms of pes anserine bursitis include swelling and tenderness of the medial region of the knee along with diffuse medial knee pain. The pain may be located along the medial joint line or posteromedial joint line which could raise suspicion of meniscus involvement. Differential diagnosis should rule out medial collateral ligament injury, medial meniscus injury, Baker’s cysts, and semimembranosus bursitis.
There is little clinical distinction between pes anserine bursitis and pes anserine tenosynovitis, but it is worth noting that bursitis tends to occur more frequently and responds quickly to treatment while tenosynovitis is less common and resistant to therapeutic intervention. Pes anserine pain syndrome, a more generic term for medial knee pain may or may not include bursitis.
Pes anserine bursitis is a clinical diagnosis where imaging is not typically required. The key to making this diagnosis is the location of tenderness. Pes anserine bursitis will be tender to palpation on the proximal medial tibia, three to five centimeters distal to the medial joint line of the knee.
Additional diagnostic criteria have not been established nor has the efficacy of using palpation to diagnose bursitis been established. Diagnostic imaging may be useful in the differential diagnosis of pes anserine bursitis. Both magnetic resonance imaging and diagnostic ultrasound can show other causes of local swelling, joint effusion, and rule out alternative diagnoses.
As with most knee pain conditions, the differential diagnosis for pain in the region of pes anserine is broad. Infectious pathology and gout should be ruled out at the initial examination. Compression to the saphenous nerve (likely through the adductor canal) can cause medial knee discomfort absent of any other pain or symptoms.
A traumatic injury can cause medial meniscus tear or medial collateral ligament rupture and stress fractures should be considered in patients who participate in repetitive sports activities such as running.
Pes anserine bursitis treatment and recovery time
Treatment for pes anserine bursitis typically follows the recommendations of other musculoskeletal conditions: rest, ice, and anti-inflammatory medications. Patients who are overweight or obese may also be deconditioned and may benefit from a program that addresses general strengthening (specifically to the quadriceps) to assist in long-term symptom improvement.
A 2016 study examined whether the presence of pes anserine tendino-bursitis was associated with greater impairment and disability in individuals with knee osteoarthritis. The study also sought to evaluate the effectiveness of local corticosteroid injection versus physical therapy.
Participants were 176 patients seen at an outpatient medical clinic and diagnosed with knee osteoarthritis. Of those included, 47% also had pes anserine tendino-bursitis.
After exclusion criteria were applied, patients with and without the condition were separated into two groups. Group A received a hot pack, ultrasound, and transcutaneous electric nerve stimulation for two weeks while Group B was given a corticosteroid injection to the most tender aspect of the pes anserine region.
Patients with osteoarthritis and pes anserine pathology had higher pain scores and more functional disability. Both physical therapy and corticosteroid injections were effective treatments for pain and no difference was found in functional ability between the two groups after treatment.
As a physical therapist, I would be remiss if I didn’t point out that a physical therapy session consisting of heat, ultrasound, and electrical stimulation is not evidence-based and should not be considered “normal.”
A similar study compared the use of Kinesio tape to physical therapy (hot pack, electrical stimulation, phonophoresis) and found both interventions were effective in the treatment of pain with kinesiotaping being the better option. It is important that readers critically evaluate research methods rather than simply reading titles and conclusions.
In both of these studies, it is possible that the results would have been different if physical therapy had addressed individual impairments (muscle tightness and weaknesses), disability, and pain levels rather than merely using passive modalities.
Robust studies evaluating the use of exercise for the treatment of pes anserine bursitis are lacking. One case study is available that describes the use of “ACL injury prevention exercises” in pes anserine syndrome.
The patient presented with decreased lower extremity strength, gait deviations, impaired knee flexion range of motion, decreased function, and pain. Though identified as exercises that are commonly used in ACL prevention, the interventions described are simply exercises that address the patient’s identified impairments.
Exercises that were utilized include dead bugs, hamstring eccentrics, squats, glute bridges, and single-leg stance with toe taps. After eight weeks, the patient showed improvements in functional mobility, pain, tenderness to palpation, range of motion, strength, flexibility, mobility, and gait. The eight-week timeline may not be desirable in cases where pain is significantly limiting other aspects of life. In these situations, corticosteroid injection can be useful as an adjunct to therapy as it allows patients to perform both activities of daily living and rehabilitation exercises that would otherwise be intolerable.
A study of corticosteroid injection alone in patients with osteoarthritis and pes anserine tendino-bursitis demonstrated that injection may be an effective first-line treatment for this condition.
Of the 17 patients, eight had a best or good response; no patient in the study was worse after the injection. This study demonstrates the utility of injections for quick pain management. Coupled with the case study on exercise intervention, it is clear that some clinicians may benefit from reconsidering a passive approach to treating this condition. There is no clear timeline for the expected recovery from pes anserine bursitis but it seems time to improvement following injection is swift.
A study of 44 patients who received either naproxen or injection found that at one-month follow-up, 58% of those taking naproxen reported significant improvement with 5% of the condition resolved, while 70% of those who were injected were significantly improved and 30% of the condition had resolved.
As with any medical condition, musculoskeletal or otherwise, readers should consult with a physician or qualified medical professional to determine the best course of treatment for their condition. This article should not be considered a substitute for professional advice or care.
Pes anserine bursitis prevention
There are no proven methods for decreasing the likelihood of developing pes anserine bursitis. As with most musculoskeletal conditions, maintaining a healthy weight and an active lifestyle may decrease the risk of developing pes anserine bursitis by staving off age-related degenerative changes that can progress to osteoarthritis and the development of type 2 diabetes. In a patient who already has type 2 diabetes, healthy diet and exercise can assist with disease management which may prevent or delay the onset of other musculoskeletal issues.
Massage therapy and pes anserine bursitis
Direct massage therapy for pes anserine bursitis is not well-supported in the scientific literature as patients with this condition are typically tender at the medial aspect of the knee and are unable to tolerate even light pressure on the area. However, there is a role for massage therapy in treating the conditions associated with pes anserine bursitis, specifically tight hamstrings and knee osteoarthritis.
A study comparing dynamic soft tissue mobilization and classic soft tissue mobilization techniques found the dynamic approach improved hamstring flexibility more in healthy males. Forty-five otherwise healthy males either received five minutes of prone lying (control group), five minutes of standard soft tissue mobilization (classic) techniques in prone or five minutes of standard (dynamic) techniques followed by longitudinal strokes during active, passive, and eccentric hamstring loading.
Post-massage therapy, participants in the dynamic group gained an average of three degrees more flexibility than those in the standard or control groups. Dynamic soft tissue mobilization techniques may be an effective treatment for patients with pes anserine bursitis when hamstring tightness is present. Hamstring tightness will likely be found in patients who report pain with full extension or demonstrate an antalgic gait as this is a compensatory mechanism to avoid pain-provoking positions.
Several studies have established the efficacy of massage therapy in patients with osteoarthritis. This investigation of the effectiveness of Swedish massage therapy in patients with knee osteoarthritis found that the treatment group improved in pain, stiffness, function, and range of motion. Changes in these variables were seen as early as three days post-intervention. This group of researchers also examined the use of Swedish massage in 68 patients with knee osteoarthritis and found it to be an efficacious treatment.
In this randomized controlled trial, participants were allocated to the intervention group (massage therapy) or the wait-list group (usual care). A standard protocol was used by the massage therapists which directed them to use effleurage, petrissage, and tapotement but did not specify the order in which the strokes should be applied. Results from this study showed patients in the intervention group had higher functional scores, less pain, and more range of motion following the intervention.
It may also be worthwhile to teach patients with knee osteoarthritis self-massage techniques to use between massage therapy sessions. A 2013 randomized control trial looked at the outcomes of self-massage intervention to the quadriceps muscles group.
Following extensive training, those in the intervention group applied self-massage twice weekly and found improvements in pain, stiffness, physical function, and knee range of motion. The techniques taught to the participants included effleurage, tapotement, and deep friction massage to address the tissues around the tendinous attachments in the knee. Engaging the patient in their treatment plan is also supported by research outside of massage therapy, specifically self-determination theory, as it increases patient autonomy by assigning them some responsibility for the management of their condition.
Pes anserine bursitis is an uncommon cause of medial knee pain. The differential diagnosis of medial knee pain should include medial collateral ligament, medial meniscus, Baker’s cyst, and pes anserine or semimembranosus bursitis. Although pes anserine bursitis is comparatively rare, it should not be overlooked, as missing this diagnosis can result in prolonged pain and unnecessary procedural interventions.