Overview
Pes anserine bursitis is inflammation or irritation of the bursa at the inner (medial) side of the knee where the hamstring tendons attach to the top of the shin bone. When this small fluid sac becomes irritated-often from overuse, friction, or altered knee mechanics-it can cause pain and tenderness along the inner knee. The discomfort may be most noticeable when walking up stairs, climbing, or rising from a chair. It can occur alone or alongside other knee problems such as osteoarthritis.
Symptoms
Patients typically notice aching or sharp pain on the inner side of the knee, usually a few inches below the joint line near the bony bump called the pes anserinus. The area is often tender to touch, and symptoms can flare with activities that load the knee, especially going up stairs, getting out of a car, or prolonged standing. Some people feel stiffness after sitting or may avoid bending the knee fully because it reproduces the pain. With persistent irritation, daily activities such as walking longer distances may become limited.
Causes
Pes anserine bursitis usually develops from repetitive stress on the medial knee, such as increased activity, hills, stairs, or improper mechanics during exercise or sports. Tightness or weakness in the hip and thigh muscles can increase strain on the hamstring attachment and the bursa. Direct pressure from kneeling or a sudden increase in training can also trigger inflammation. In some cases, underlying knee conditions such as osteoarthritis contribute by changing how forces travel through the joint.
Risk Factors
Risk is higher in people who have frequent or sudden increases in walking, stair use, running, or sports that load the inner knee. Tight hip muscles, weak hip abductor strength, and knee alignment issues such as "knock-knee" (increased valgus) can contribute. Being overweight increases stress on the knee structures, and older age with degenerative knee changes can make the area more vulnerable. Prior knee injuries and repetitive kneeling at work or during hobbies can also raise risk.
Prevention
You can reduce recurrence by keeping activity increases gradual and avoiding sudden spikes in stair climbing, running, or hills. Strengthening the hip and thigh muscles-especially hip abductors-and improving flexibility can help unload the pes anserine region. Using supportive footwear, maintaining healthy body weight, and adjusting technique during exercise (such as knee alignment and stride) can lower repetitive stress. If symptoms start to flare, temporarily scaling back the aggravating activity and focusing on mobility and controlled strengthening often helps.
How the Diagnosis Is Evaluated
Clinicians typically diagnose pes anserine bursitis based on your symptoms and a focused physical exam, including pinpoint tenderness at the medial pes anserinus area and pain reproduced with specific knee movements or resisted hamstring activity. The exam also checks for related causes of inner knee pain, such as meniscus injury, MCL sprain, or medial joint line osteoarthritis. Imaging is not always required, but ultrasound can confirm bursitis and rule out some alternatives. X-rays may be used to assess for osteoarthritis, and MRI is considered when the diagnosis is unclear or symptoms suggest deeper knee injury.
Nonsurgical Treatment Options
Most cases improve with conservative care focused on reducing irritation and restoring mechanics. Activity modification, relative rest during flares, and short-term ice or anti-inflammatory measures can help calm pain and swelling. Physical therapy commonly plays a central role, using stretching and progressive strengthening of the hip and thigh muscles plus guidance on gait and exercise form. Over-the-counter or prescription NSAIDs may be used if appropriate for you, along with supportive measures such as knee-friendly footwear or temporary avoidance of kneeling. If pain persists despite therapy, a corticosteroid injection into the tender pes anserine bursa may provide targeted relief. In stubborn cases, some clinicians may consider platelet rich plasma (PRP) injections, though evidence and suitability vary by patient.
When to Seek Medical Attention
Seek prompt medical attention if you have fever, significant redness or warmth over the inner knee, or rapidly increasing swelling, because infection or another urgent problem must be ruled out. Get evaluated urgently if you cannot bear weight, the pain becomes severe and sudden, or symptoms are associated with numbness, new weakness, or trouble controlling bowel or bladder function. Also seek care soon if calf swelling or marked calf pain occurs with knee symptoms, since blood clots can mimic knee problems. Otherwise, arrange a timely outpatient visit if inner knee pain persists beyond a couple of weeks despite home measures.
Frequently Asked Questions
Pes anserine bursitis usually causes localized tenderness below the inner knee and pain that is reproduced with hamstring-related movements, while a sprain more often follows a twisting injury with ligament-specific pain.
Many people improve within several weeks with consistent conservative care, but healing can take longer if mechanics and muscle strength are not addressed.
Next Steps
If you have pinpoint inner-knee tenderness and pain with stairs or rising from a chair, start by reducing the aggravating activity and scheduling an evaluation for an accurate diagnosis. A clinician can confirm that it is pes anserine bursitis and tailor physical therapy and pain control to your knee mechanics and overall health.