Snapshot An obese 47-year-old woman with diabetes presents to her orthopedist reporting left medial knee pain for the past 6 months. She denies any inciting injury or trauma. The pain is worse when she climbs stairs or rises from a seated position. On physical exam, there is tenderness to palpation over the anteromedial proximal tibia. A radiograph reveals no fracture and a follow-up magnetic resonance imaging of the left knee shows fluid accumulation around the pes anserine bursa. Introduction Clinical definition inflammation of the medial knee that often coexists with other knee disorders and is characterized by spontaneous pain Epidemiology demographics female > male common in young adults who actively do sports common in overweight middle-aged women common in older adults with osteoarthritis location the pes anserine bursa and its tendons are located along the medial proximal aspect of the tibia risk factors female sex diabetes obesity valgus knee deformity Etiology tight hamstrings acute trauma or athletic overuse degenerative processes Pathogenesis extra stress or friction can cause irritation and inflammation of the bursa, the associated tendons, or the pannus (especially in obese individuals) currently, it is unclear which structure surrounding the pes anserine bursa is responsible for the symptoms trauma can also cause inflammation in the area Associated conditions Osgood-Schlatter syndrome osteoarthritis Prognosis self-limited and responds well to exercises and stretches time to resolution varies from weeks to years Presentation Symptoms mild or moderate knee pain when arising from a seated position climbing stairs pain is worse at night Physical exam tenderness and swelling of the proximal medial tibia 6-7 cm below the anteromedial joint line of the knee may have palpable crepitus shortened hamstring to popliteal angle Imaging Radiography indication only indicated to rule out proximal tibial stress fracture if there is any clinical suspicion recommend views anteroposterior and lateral findings typically normal Magnetic resonance imaging indication only indicated if diagnosis and radiograph is unclear findings increased signal intensity fluid accumulation around the bursa Studies Diagnostic injection with lidocaine or lidocaine-corticosteroids alleviation of pain with injection suggests the diagnosis of pes anserine bursitis Making the diagnosis most cases are clinically diagnosed Differential Tibial stress fracture distinguishing factor very severe pain over proximal tibia Medial meniscus injury distinguishing factors often presents with knee locking or catching positive McMurray test Treatment Conservative rest and physical therapy indication for all patients modalities stretching of pes anserine tendons Medical nonsteroidal anti-inflammatory drugs (NSAIDs) indication pain management intrabursal injection with lidocaine and/or corticosteroids indication second-line pain management Complications Persistent pain