Bursa is a small, closed, fluid-filled synovial sac interposed between anatomical structures — most commonly between tendons, muscles, skin, and underlying bony prominences — that functions as a mechanical buffer to reduce friction and absorb compressive forces during movement. Unlike a joint capsule, which encloses an articular space between two bones, a bursa is an independent, extrasynovial structure that does not communicate with the joint cavity unless pathologically ruptured or congenitally connected. The sac is lined by a specialized synovial membrane that secretes and reabsorbs a small volume of lubricating fluid (synovial fluid), maintaining near-frictionless gliding between adjacent structures. Bursae exist as either anatomic bursae (present at birth, constant across individuals — e.g., subacromial, olecranon, prepatellar) or adventitious bursae (acquired in response to chronic external pressure or friction at atypical sites — e.g., over a bunion or bony prominence in an amputee’s residual limb). When the synovial lining becomes inflamed — from trauma, overuse, infection, gout, or systemic inflammatory disease — the condition is termed bursitis, characterized by excessive fluid accumulation, pain, swelling, and restricted range of motion (ICD-10-CM M70-M71 range). Bursa is commonly confused with ganglion cyst, which arises from joint or tendon sheath connective tissue and lacks a true synovial lining, and with synovial cyst, which communicates directly with an adjacent joint space.
Noun-forming suffix — denotes a singular feminine noun in the first declension; plural becomes bursae
The word entered English in the 1690s as bursa (noun), borrowed directly from Medieval Latin bursa (“pouch, purse”), from Greek byrsa (“hide, wine-skin, pouch”) — literally “a little purse or pouch.” The anatomical use was adopted by early anatomists who noted the structural resemblance of the fluid-filled sac to a drawstring purse. The root burs- (“pouch”) connects bursa to the entire -burs- ROOT FAMILY: bursitis (burs- + -itis → inflammation of the bursa), bursar (burs- → treasurer, keeper of the purse), and bursa of Fabricius (lymphoid organ in birds, named by Hieronymus Fabricius, 1621). The suffix -a marks this as a Latin first-declension feminine noun; its plural bursae is the form used in anatomical nomenclature and should be recognized when encountered in operative and pathology reports.
🔀 ALIASES / ALTERNATE TERMS
Bursal(adjective form — appears clinically as “bursal fluid,” “bursal inflammation,” “bursal injection,” “bursal thickening” on imaging reports)
Synovial bursa(anatomically precise synonym emphasizing the synovial lining; distinguishes true bursae from adventitious or non-synovial sacs)
Bursal sac(descriptive lay/clinical term used in operative notes and patient education; coded under the same M70-M71 range depending on site and etiology)
Bursae(Latin plural form; used in anatomical nomenclature, pathology reports, and imaging — e.g., “bilateral subacromial bursae”)
Adventitious bursa(acquired bursa that forms at sites of chronic pressure or friction not typically containing a bursa; common in amputee residual limbs, bunion sites, and pressure injury-prone bony prominences; coded as other bursitis NEC — M71.3x)
Retrocalcaneal bursa(anatomic bursa located between the Achilles tendon and the calcaneus; inflammation coded as M77.3x — retrocalcaneal bursitis)
Subacromial bursa(largest and most clinically significant bursa in the shoulder, located between the rotator cuff and the acromion; inflammation coded as M75.5x — subacromial bursitis)
Olecranon bursa(anatomic bursa overlying the olecranon process of the ulna at the elbow; inflammation coded as M70.2x — olecranon bursitis)
Prepatellar bursa(anatomic bursa anterior to the patella; classic occupational bursitis — “housemaid’s knee”; coded as M70.4x)
Infrapatellar bursa(anatomic bursa inferior to the patella, superficial or deep; inflammation coded as M70.5x — infrapatellar bursitis)
Trochanteric bursa(anatomic bursa overlying the greater trochanter of the femur; inflammation coded as M70.6x — trochanteric bursitis; high-frequency code in PM&R)
Ischial bursa(anatomic bursa over the ischial tuberosity; inflammation coded as M70.7x — other bursitis of hip; relevant in wheelchair-dependent patients)
🔗 RELATED TERMS
Bursitis — the pathological state of bursa; inflammation of the synovial lining resulting in excessive fluid production, pain, warmth, and swelling; principal ICD-10-CM codes in the M70-M71 range with site-specific and laterality subcategories
Synovium — shares the synovi- root with synovial cyst and synovial fluid; the specialized secretory lining membrane common to both bursae and joint capsules; its inflammation (synovitis) may coexist with bursitis
Synovial cyst — closely related fluid-filled structure, but communicates directly with an adjacent joint space, distinguishing it from a true bursa; common sites include the popliteal fossa (Baker’s cyst, M71.2x) and wrist
Ganglion cyst — a mucinous cyst arising from joint or tendon sheath connective tissue, lacking a true synovial lining; frequently confused with bursal pathology on clinical exam; coded M67.4x
Bursectomy — surgical excision of an inflamed or chronically thickened bursa; performed when conservative management fails; relevant CPT codes include 27060 (ischial) and 27062 (trochanteric)
Tendon — the primary anatomical neighbor of most bursae; bursae exist specifically to reduce friction between tendons and underlying bony surfaces; concurrent tendinitis and bursitis frequently coexist and may both require coding
Synovial fluid — the lubricating secretion produced by the synovial lining of the bursa; aspiration and laboratory analysis of bursal fluid is used to differentiate septic bursitis, gout, pseudogout, and inflammatory arthritis
Septic bursitis — infectious bursitis most commonly caused by Staphylococcus aureus; coded M71.0x (right) or M71.02 (elbow); requires specific documentation of organism for most specific coding and CC/MCC capture
Gout — systemic purine metabolism disorder causing urate crystal deposition within bursae and joint spaces; acute gouty bursitis is a high-frequency coding scenario in inpatient PM&R and orthopedics (M10.0x-M10.9x)
Calcific bursitis — bursitis complicated by calcium hydroxyapatite crystal deposition within the bursal sac; associated with rotator cuff calcific tendinopathy; coded M71.4x (calcium deposit in bursa)
Aspiration/injection, bursa — key diagnostic and therapeutic procedure; bursal aspiration yields fluid for culture and crystal analysis; corticosteroid injection is first-line treatment for non-infectious bursitis; CPT 20610-20611
CODING CORNER
🏥 ICD-10-CM CODES
Soft Tissue Disorders Related to Use, Overuse, and Pressure — Bursitis (M70.x)
Code
Description
M70.20
Olecranon bursitis, unspecified elbow
M70.21
Olecranon bursitis, right elbow
M70.22
Olecranon bursitis, left elbow
M70.30
Other bursitis of elbow, unspecified elbow
M70.31
Other bursitis of elbow, right elbow
M70.32
Other bursitis of elbow, left elbow
M70.40
Prepatellar bursitis, unspecified knee
M70.41
Prepatellar bursitis, right knee
M70.42
Prepatellar bursitis, left knee
M70.50
Other bursitis of knee, unspecified knee
M70.51
Other bursitis of knee, right knee
M70.52
Other bursitis of knee, left knee
M70.60
Trochanteric bursitis, unspecified hip
M70.61
Trochanteric bursitis, right hip
M70.62
Trochanteric bursitis, left hip
M70.70
Other bursitis of hip, unspecified hip
M70.71
Other bursitis of hip, right hip
M70.72
Other bursitis of hip, left hip
M70.811
Bursitis of right shoulder (use overuse)
M70.812
Bursitis of left shoulder (use overuse)
M70.819
Bursitis of unspecified shoulder (use overuse)
Other Bursitis and Bursopathies (M71.x)
Code
Description
M71.00
Abscess of bursa, unspecified site
M71.011
Abscess of bursa, right shoulder
M71.012
Abscess of bursa, left shoulder
M71.021
Abscess of bursa, right elbow
M71.022
Abscess of bursa, left elbow
M71.031
Abscess of bursa, right wrist
M71.032
Abscess of bursa, left wrist
M71.041
Abscess of bursa, right hand
M71.042
Abscess of bursa, left hand
M71.051
Abscess of bursa, right hip
M71.052
Abscess of bursa, left hip
M71.061
Abscess of bursa, right knee
M71.062
Abscess of bursa, left knee
M71.071
Abscess of bursa, right ankle and foot
M71.072
Abscess of bursa, left ankle and foot
M71.08
Abscess of bursa, other site
M71.09
Abscess of bursa, unspecified site (NOS)
M71.10
Other infective bursitis, unspecified site
M71.111
Other infective bursitis, right shoulder
M71.112
Other infective bursitis, left shoulder
M71.121
Other infective bursitis, right elbow
M71.122
Other infective bursitis, left elbow
M71.131
Other infective bursitis, right wrist
M71.132
Other infective bursitis, left wrist
M71.141
Other infective bursitis, right hand
M71.142
Other infective bursitis, left hand
M71.151
Other infective bursitis, right hip
M71.152
Other infective bursitis, left hip
M71.161
Other infective bursitis, right knee
M71.162
Other infective bursitis, left knee
M71.171
Other infective bursitis, right ankle and foot
M71.172
Other infective bursitis, left ankle and foot
M71.18
Other infective bursitis, other site
M71.19
Other infective bursitis, unspecified site
M71.20
Synovial cyst of popliteal space (Baker’s cyst), unspecified knee
M71.21
Synovial cyst of popliteal space (Baker’s cyst), right knee
M71.22
Synovial cyst of popliteal space (Baker’s cyst), left knee
M71.30
Other bursal cyst, unspecified site
M71.311
Other bursal cyst, right shoulder
M71.312
Other bursal cyst, left shoulder
M71.321
Other bursal cyst, right elbow
M71.322
Other bursal cyst, left elbow
M71.40
Calcium deposit in bursa, unspecified site
M71.411
Calcium deposit in bursa, right shoulder
M71.412
Calcium deposit in bursa, left shoulder
M71.421
Calcium deposit in bursa, right elbow
M71.422
Calcium deposit in bursa, left elbow
M71.50
Other bursitis, not elsewhere classified, unspecified site
MRSA as the cause of diseases classified elsewhere (use with M71.1x for septic bursitis)
B95.8
Unspecified staphylococcus as the cause of diseases classified elsewhere
🔧 COMMON CPT CODES (Bursa-Related Diagnosis & Treatment)
CPT Code
Description
20600
Arthrocentesis, aspiration and/or injection, small joint or bursa — without ultrasound guidance
20604
Arthrocentesis, aspiration and/or injection, small joint or bursa — with ultrasound guidance, with permanent recording and reporting
20610
Arthrocentesis, aspiration and/or injection, major joint or bursa (e.g., shoulder, hip, knee, subacromial bursa) — without ultrasound guidance
20611
Arthrocentesis, aspiration and/or injection, major joint or bursa — with ultrasound guidance, with permanent recording and reporting
27060
Excision of ischial bursa
27062
Excision of trochanteric bursa or calcification
23044
Arthrotomy, glenohumeral joint, with removal of loose body or foreign body — includes subacromial bursa exploration
29826
Arthroscopy, shoulder, surgical; with decompression of subacromial space with partial acromioplasty, with coracoacromial ligament (e.g., arch) release, when performed (includes bursectomy)
Ultrasonic guidance for needle placement, imaging supervision and interpretation (use with 20610/20611 when billed separately — check bundling)
⚠️ Coding Note: Site specificity and laterality are required for all M70-M71 codes — unspecified laterality codes (e.g., M70.60) should be queried if documentation supports a specific side, as payers including UnitedHealthcare and Aetna increasingly flag unspecified laterality on professional claims. Sequence the underlying condition first when bursitis is a manifestation of gout (M10.0x), rheumatoid arthritis (M05-M06), or infection (M71.0x-M71.1x), with the bursal code as an additional diagnosis. A common undercoding alert in PM&R inpatient stays: trochanteric bursitis (M70.6x) is frequently documented only as “hip pain” or “greater trochanter tenderness” — both phrases should trigger a physician query to clarify whether bursitis has been diagnosed, as M70.61/M70.62 are significantly more specific and support stronger DRG coding than R10 or M25.55x pain codes. For septic bursitis, always append the causative organism code (B95-B97 range) per ICD-10-CM instructional note at M71.0x; MRSA bursitis (M71.1x + B95.62) captures an MCC in most MS-DRG groupings. CPT 20611 (ultrasound-guided major bursa injection) is increasingly required by BCBS of Wisconsin and UMR for shoulder and hip bursal injections — confirm that permanent imaging documentation exists before billing, as this is a common audit trigger.
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