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Function of Pes Anserinus Muscles
The primary function of the muscles forming the pes anserinus is to flex the knee joint, medially rotate the thigh, and dynamically stabilize the knee, preventing valgus alignment. This condition is common among long-distance runners, where excessive friction can lead to local inflammation of periarticular structures, such as bursae and tendons of the hamstring muscles.
Pes Anserinus Syndrome – Symptoms
Typical symptoms of pes anserinus syndrome include:
- Pain localized on the medial side of the knee, often occurring at night.
- Morning stiffness lasting longer than an hour.
- Tenderness upon touch or localized swelling.
- Pain that intensifies when climbing stairs, sitting down, standing up, or getting out of a car.
These symptoms do not have to occur simultaneously to diagnose inflammation in the pes anserinus region. Some individuals only experience symptoms during running, when tendon insertions are irritated by improper lower limb biomechanics or poor running technique.
Depending on the efficiency of muscles controlling lower limb biomechanics, pain may arise at the beginning, during, or at the end of a run. Training intensity also plays a role—an increase in workload can trigger symptoms. Precise diagnosis is essential, as symptoms may also originate from:
- Damage to the medial meniscus,
- Degenerative changes in the medial compartment of the knee joint,
- Injury to the medial collateral ligament,
- Inflammation of the fat pad in the medial knee region.
Dominant Symptoms of Pes Anserinus Inflammation
Moderate pain intensity,
Pain that worsens with physical activity and is most uncomfortable in the morning,
Increased tension in pes anserinus muscles,
Localized swelling.
Pes Anserinus Syndrome – Causes
The cause often lies in the biomechanics of the femur, such as:
- Increased anterior pelvic tilt,
- Internal rotation of the femur,
- Excessive pronation of the rearfoot.
These factors predispose individuals to injury and manifest as valgus knees, excessive forward bending at the hips during running, or collapsing of the foot's longitudinal arch. The syndrome frequently results from a combination of valgus knees and ligament instability confirmed by specialized orthopedic tests.
The root cause of misaligned bone structures during dynamic movement often includes weakened strength and endurance in the pelvic girdle muscles, hamstring group, quadriceps, and hip adductors. Another critical factor is the ability of the hamstring muscles to perform eccentric work (controlled muscle lengthening), which is essential for maintaining proper control of the lower leg during deceleration of forward movement in the leading limb during running.
Common causes of pes anserinus inflammation, particularly among runners, include:
Training errors (e.g., lack of warm-up),
Overtraining,
Continuing to train despite evident knee dysfunction and limited range of motion,
Improper exercise technique,
Poorly fitted running shoes.
How to Treat Pes Anserinus Syndrome?
In the initial stages, when pain is significant, training loads should be reduced to avoid provoking or exacerbating symptoms. Pain relief strategies include icing the painful area and placing a pillow between the knees while sleeping. Physiotherapy involves:
Relaxing the muscles forming the pes anserinus,
Stretching,
Strengthening exercises for the hip adductors and quadriceps, particularly the vastus medialis muscle.
When selecting exercises, biomechanical analysis of the body is essential to identify the underlying cause of symptoms. Functional tests are often employed by physiotherapists for this purpose.
Exercises for Pes Anserinus Syndrome
Hip Flexor Stretch
Kneel on one leg, ensuring the pelvis is properly aligned by tucking the tailbone under.
Shift the torso forward to stretch the front of the thigh.
Gluteal Muscle Stretch
Sit with one leg straight and the other bent at the knee, positioned across the straight leg.
Keep the spine upright and rotate the torso toward the bent leg to feel a stretch in the gluteal muscles.
Inner Thigh Stretch
Sit with legs spread wide and knees straight.
Keep the lumbar spine upright and twist the torso.
Hamstring Stretch
Lie on your back with one leg flat on the floor.
Rest the other leg against a wall, keeping the knee straight and the thigh vertical.
Hold this position for 30-40 seconds.
How Long Does Pes Anserinus Treatment Take?
Treatment begins with rehabilitation and physiotherapy, including anti-inflammatory and pain-relieving therapies, manual therapy, and stretching. If no significant improvement is observed after 4-6 weeks, and ultrasonography confirms the condition, a corticosteroid injection into the bursa may be considered.
Corticosteroid Injection
The injection can be administered under ultrasound guidance for precision, though this is not always necessary for pes anserinus syndrome. An orthopedic specialist typically administers a single injection, sufficient to alleviate symptoms or reduce them to a manageable level for further rehabilitation. In more severe cases, up to three injections may be given at intervals of several weeks. After the injection, physical activity should be avoided for about a week. For professional athletes, a shorter break of 2-3 days may suffice. If ultrasonography shows fluid in the bursa, drainage may be performed using a syringe.
How to Prevent Pes Anserinus Syndrome?
Prevention involves correcting biomechanical alignment through exercises tailored by a physiotherapist and improving running biomechanics. Consulting a coach to develop a suitable training regimen, including both running and strength conditioning with individualized loads, is also recommended.
Where to Seek Help for Pes Anserinus Syndrome?
If you suspect you have pes anserinus syndrome and rest or a break from training has not helped, it is time to consult a specialist. Our physiotherapists and orthopedic specialists are available to assist you in Warsaw, Poznań, Gdańsk, and Konin.
Related Articles
Explore other potential causes of knee pain in different parts of the joint.
References:
- National Library of Medicine - "Pes Anserine Bursitis" - Michael Mohseni, Charles Graham
- Sports Injury Bulletyn - "Uncommon injuries: medial knee pain from the pes anserinus - part I" - Andrew Hamilton
- Wydawnictwo Lekarskie PZWL - "Medycyna sportowa - Współczesne metody diagnostyki i leczenia" - Patrick J. McMahon
