Prepatellar bursitis is a common and treatable condition that causes the front of your knee to swell. It happens when the bursa sac in front of your knee cap becomes inflamed. Most cases of prepatellar bursitis can be treated from home with rest. Prepatellar bursitis that is caused by an injury will usually go away on its own. The body will absorb the blood in the bursa over several weeks, and the bursa should return to normal. If swelling in the bursa is causing a slow recovery, a needle may be inserted to drain the blood and speed up the process.
Bursitis is often mistaken for arthritis because joint pain is a symptom of both conditions. There are various types of arthritis that cause joint inflammation, including the autoimmune response of rheumatoid arthritis or the breaking down of cartilage in the joints in degenerative arthritis. If a septic bursitis is left untreated, the fluid inside the bursa can turn to pus. In addition, the infection can spread to the bloodstream and other parts of the body. If the infection spreads, symptoms will become worse and the infection can even become life-threatening.
Other Names
- Housemaid’s knee
- Carpenter’s knee
- Prepatellar Bursitis (PPB)
- Infectious Prepatellar Bursitis
- Noninfectious Prepatellar Bursitis
- Aseptic Prepatellar Bursitis
- Coal miner’s knee
- Carpet layer’s knee
- Hemorrhagic bursitis
Pathophysiology
- General
- Poorly described in the literature thus much of the discussion, on management is extrapolated from other bursopathies
- Occurs due to friction between the dermal layers and patella, or compressive forces from direct trauma
- Noninfectious/ Aseptic
- Represents the majority of cases
- Common etiologies include trauma, crystal deposition, or systemic inflammatory diseases
- Infectious
- Between 20-30% are septic
- Typically skin lesions
- Less commonly, can also arise spread primary cellulitis and in rare cases, from hematogenous
- Common bacteria: Staphylococcus aureus (#1), Brucella sp.
- Uncommon pathogens: fungi, tuberculosis
- Up to 50% of all SB cases occur in immunocompromised patients (need citation)
- #2 location for septic bursitis behind the olecranon, which is 4x more common
- Hemorrhagic
- Can occur due to trauma or in patients on anticoagulation
Causes
- Trauma
- Most commonly due to chronic, repetitive microtrauma
- Can be due to acute trauma
- Typically aseptic unless violation of soft tissue
- Crystal deposition
- Including gout, pseudogout causing aseptic, inflammatory
- Systemic inflammatory diseases
- Includes rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, or uremia
Pathoanatomy
- Prepatellar Bursa
- Located between the Patella and overlying subcutaneous tissue
- Sports
- Wrestling
- Volleyball
- Baseball and Softball catchers
- Occupations
- Common in occupations requiring kneeling
- Housekeeping
- Plumbing
- Carpet installers
- Gardening
- Roofing
- Autoimmune and Inflammatory
- Gout
- Rheumatoid Arthritis
Differential Diagnosis
- Fractures
- Distal Femur Fracture
- Patellar Fracture
- Tibial Plateau Fracture
- Dislocations & Subluxations
- Patellar Dislocation (and subluxation)
- Knee Dislocation
- Proximal Tibiofibular Joint Dislocation
- Muscle and Tendon Injuries
- Quadriceps Contusion
- Iliotibial Band Syndrome
- Quadriceps Tendonitis
- Patellar Tendonitis
- Popliteus Tendinopathy
- Extensor Mechanism Injury
- Patellar Tendon Rupture
- Quadriceps Tendon Rupture
- Patellar Fracture
- Ligament Pathology
- ACL Injury
- PCL Injury
- MCL Injury
- LCL Injury
- Meniscal Pathology
- Posterolateral Corner Injury
- Multiligament Injury
- Arthropathies
- Knee Osteoarthritis
- Septic Arthritis
- Gout
- Bursopathies
- Prepatellar Bursitis
- Pes Anserine Bursitis
- MCL Bursitis
- Infrapatellar Bursitis
- Patellofemoral Pain Syndrome (PFPS)/ Anterior Knee Pain)
- Chondromalacia Patellae
- Patellofemoral Osteoarthritis
- Osteochondral Defect Knee
- Plica Syndrome
- Infrapatellar Fat Pad Impingement
- Patellar Instability
- Neuropathies
- Saphenous Nerve Entrapment
- Other
- Bakers Cyst
- Patellar Contusion
- Pediatric Considerations
- Patellar Apophysitis (Sinding-Larsen-Johansson Disease)
- Patellar Pole Avulsion Fracture
- Tibial Tubercle Avulsion Fracture
- Tibial Tuberosity Apophysitis (Osgood Schalatters Disease)
Diagnosis
- History
- Typically some sort of repetitive microtrauma
- Maybe an acute trauma
- Patients will endorse knee pain, anterior swelling
- Trouble ambulating
- Physical Exam
- Obvious swelling of the prepatellar bursa
- Overlying erythema, warmth is often present
- The prepatellar space will be tender with fluctuance, edema, crepitus
- Range of motion is often restricted
- Notably absent is a joint effusion
- Septic vs aseptic can be difficult to distinguish clinically
- Special Tests
Knee ultrasound demonstrating edema, cobblestoning, and acute bursal fluid collection
Radiographs
- Standard Radiographs Knee
- Typically Normal
- Used to exclude other pathology
- Potential findings
- Prepatellar soft tissue swelling
- Calcifications in the prepatellar soft tissues in more chronic cases[9]
Ultrasound
- Findings
- Hypoechoic fluid collection anterior to patella[10]
- May have heterogenous debris
- Also useful to guide aspiration or injection if indicated
MRI
- Not typically indicated
- Potential Findings
- Low T1, bright T2/STIR signal intensity
- Wall of bursa may be thickened, irregular
Laboratory
- Labs are not typically indicated
- However, if septic bursitis is a consideration, then labs are indicated
- Aspiration: Fluid analysis, gram stain, culture, glucose, protein, lactate
- Serum: CBC, ESR, CRP
| Characteristic | Appearance | WBC (per µL) | Differential count | Bursal fluid–to–serum glucose ratio | Gram stain | Culture |
| Septic bursitis (SB) | Purulent | 1500-300,000; mean 75,000 | Polymorphonuclear (PMN) cells | < 50% | Positive in 70% | Positive |
| Nonseptic bursitis (NSB) | Serosanguineous, straw-colored, or bloody | 50-10,000; usually < 3000 | Predominantly mononuclear cells | >50% | Negative | Negative |
Treatment
Treatment typically involves resting the affected joint and protecting it from further trauma. In most cases, bursitis pain goes away within a few weeks with proper treatment, but recurrent flare-ups of bursitis are common.
Prognosis
- Most cases will be completely resolve with prompt, appropriate treatment
- No large scale studies evaluating the prognosis of PPB
Nonoperative
- Indications
- Inflammatory and non-infectious
- Compression
- Knee Compression Sleeve
- Analgesics
- NSAIDS
- Aspiration
- Not typically recommended as first line therapy
- Indicated if septic bursitis is a consideration
- Corticosteroid Injection
- Can be considered in refractory cases
- No clear guidelines or evidence
- Consider
- Physical Therapy if recovery is slow or delayed
- Occupational Therapy directed at activity modification
- Knee Pads for occupations where repetitive microtrauma occurs due to kneeling
- Septic Bursitis
- Antibiotics with gram positive coverage
- Orthopedic surgery consultation
Operative
- Indications
- Failure of conservative treatment
- Septic bursitis
- Technique
- Open vs arthroscopic Bursectomy
- Irrigation and debridement
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