What are the large bursas in the human body?

Large Bursae in the Human Body

The major large bursae in the human body include the trochanteric, iliopsoas, subacromial, olecranon, prepatellar, and popliteal (Baker's) bursae, which are clinically significant due to their size and frequency of pathological involvement.

Anatomical Distribution of Major Bursae

Hip Region

• Trochanteric bursa: Located at the greater trochanter of the femur, this large bursa can become inflamed causing lateral hip pain 1, 2
• Iliopsoas bursa: Located anterior to the hip joint, between the iliopsoas tendon and femoral head 2

Knee Region

• Prepatellar bursa: Located anterior to the patella, between the skin and patellar tendon 3, 4
• Popliteal bursa (Baker's cyst): Located in the posterior knee between the gastrocnemius and semimembranosus muscles; frequently communicates with the knee joint space 1
  • Can extend far into thigh and calf muscles when enlarged
  • Rupture may clinically mimic deep vein thrombosis

Shoulder Region

• Subacromial bursa: The main bursa of the shoulder, facilitating normal movement between the acromion and rotator cuff 5
  • Has a lateral subdeltoid part and a variable subcoracoid portion
  • Well-innervated structure

Elbow Region

• Olecranon bursa: Located at the posterior aspect of the elbow over the olecranon process 4

Clinical Significance

Diagnostic Imaging

• Ultrasound is particularly useful for evaluating bursae due to their superficial location 6, 4

  • Characteristics of normal bursae: thin-walled, compressible structures with minimal fluid
  • Pathological bursae typically appear as fluid collections that are unilocular and compressible

• MRI is the most accurate imaging method for assessing:

  • Wear-induced synovitis 1
  • Peritrochanteric structures including the gluteus muscles and trochanteric bursa 2

Common Pathologies

• Bursitis: Inflammation of bursae that can result from:

  • Acute trauma
  • Overuse syndromes
  • Inflammatory conditions (rheumatoid arthritis, gout)
  • Infections 6

• Popliteal cysts (Baker's cysts):

  • Fluid accumulation in the bursa between gastrocnemius and semimembranosus muscles
  • Can be visualized sonographically in the posterior transverse scan 1

• Trochanteric bursitis:

  • May coexist with gluteus medius tendinosis
  • Can be misinterpreted as other conditions in patients with hip arthroplasty 2

Clinical Pearls

• Bursae can be classified as native (lined with synovial membrane at predictable anatomical sites) or adventitious (formed at sites of friction) 4

• When evaluating bursal pathology, there is often overlap in imaging findings regardless of cause 4

• Ultrasound characteristics of distended bursae include:

  • Fluid collection with simple anechoic or complex hypoechoic fluid
  • Unilocular and compressible nature (unlike ganglion cysts which are typically multilocular and non-compressible) 4

• Massive enlargement of bursae can occur in certain conditions, as documented in case reports of massive prepatellar bursae 7