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Bursitis of the knee and hip

Description

Bursitis is an inflammation or degeneration of the sac-like structures that protect the soft tissues from bony prominences.  Many areas of the body contain a bursa, including the shoulders, ankles, hips, and knees.  Bursitis may result from local injury or systemic diseases.  Examples of systemic disease include rheumatoid arthritis, tophaceous gout, and septic bursitis. 

This topic will explore the manifestations and treatment specific to knee and hip bursitis.  The most common forms of knee bursitis involveaq the anserine bursa, prepatellar bursa, and infrapatellar bursa.  The most common hip bursitis involves the trochanteric bursa. 

Clinical manifestations

The presence of bursitis is usually suspected on clinical grounds.  The most common features of bursitis include pain on motion and at rest, swelling if close to body surface, and local tenderness.  There may be loss of range of motion, depending on the site involved.   

Patients most at risk for bursitis from local injury will describe aggravating factors such as repetitive direct pressure to an underlying bursa.  Other risk factors include obesity, compression injury, or other minor local trauma. 

Prepatellar bursitis

A prepatellar bursitis is an inflammation of the largest knee bursa, located between the patella and the underlying skin.  Most commonly it is caused by trauma.  Falls or direct pressure may aggravate this bursitis, as will repetitive kneeling (“housemaid’s knee”).  This bursa is commonly one that can become infected. 

Patients with prepatellar bursitis complain of knee swelling and pain over the front of the knee.  A clinical diagnosis can be made by simple inspection and palpation of the anterior knee.  To determine the etiology of prepatellar bursitis, bursal fluid aspiration and analysis may be necessary.  On physical exam, the bursa is described as a cystic, ballotable collection of fluid directly over the patella.  Inflammatory signs are variable (erythema, warmth) and depend on the chronicity of the bursitis.  A distinguishing feature from a knee joint effusion is that bursitis is extra-articular and therefore the range of motion of the knee is not typically impaired. 

Anserine bursitis

Anserine bursitis is located medially, about 6 cm below the joint line between the attachment of the medial collateral ligament at the medial tibial plateau and the conjoined tendon of the gracilis, sartorius, and semitendinosus tendons.  The most common problem associated with anserine bursitis is the presence of osteoarthritis (medial compartment) and abnormal gait.  Increased pressure and friction, from any gait disturbance affecting the knee, hip, and pelvis, can result in this form of bursitis. 

Clinically, anserine bursitis presents with pain, particularly at night, and in the medial knee region.  Typically, patients can point directly at the area with their finger when asked where the pain is worst.  Physical exam to rule out an underlying medial collateral ligament problem can be performed with a valgus stress test.  Anserine bursitis is usually described as a quarter-sized area of tenderness at the level of the tibial tubercle approximately 1.5 inches below the medial joint line. 

Infrapatellar bursitis

Infrapatellar bursitis is located just below the kneecap.  It is often referred to as “clergyman’s bursitis” due to the historical frequency among clergyman after injury while kneeling on hard surfaces for prayer.  There are deep and superficial infrapatellar bursae.  The pain may be similar to patellar tendinitis.  The deep bursa lies between the patellar ligament and the upper front surface of the tibia.  The superficial bursa is located between the patellar ligament and the skin.  Pain and swelling on physical examination at this location of the knee helps to differentiate this bursitis from prepatellar bursitis. 

Trochanteric bursitis

The deep trochanteric bursa is located between the tendon of the glueus medius and the posterolateral prominence of the greater trochanter.  A more superficial trochanteric bursa is located directly over the greater trochanter and can become inflamed and tender as well.  The characteristic symptom is of night pain while lying on the affected side.  Walking may be affected.  It may occur in association with hip osteoarthritis. 

Gait disturbances can contribute to the direct pressure and repetitively aggravate the bursa.  Common gait abnormalities associated with trochanteric bursitis include lumbosacral spine disease, leg-length discrepancy, sacroiliac joint disorders, knee arthritis, and ankle sprain.  Diagnosis is usually made by palpation of the area and assessment of the hip, spine, lower back, and lower extremity.  Local tenderness is felt on palpation at the level of the greater trochanter.

Red flags

Septic bursitis can occur and requires identification of the organism with appropriate antibiotic coverage.  More than 80% of cases of septic bursitis are caused by Staphylococcus aureus and other Gram-positive organisms.  The Gram stain may not be positive in all cases; therefore, a high level of clinical suspicion is needed to appropriately treat.  Risk factors for septic bursitis include diabetes mellitus, steroid therapy, alcoholism, uremia, and trauma.  Septic bursitis most commonly occurs from trauma or overlying cellulitis of the skin.

Epidemiology

The epidemiology of bursitis is unclear, and reliable data for incidence, age, and sex predilection or geographic spread are not available.  Bursitis accounts for 0.4% of primary care clinic visits.  The incidence of bursitis may be higher in runners (10%).  A small retrospective Spanish study showed 40 patients with confirmed superficial septic bursitis were found to be predominantly male (80%) with a mean age of 52 years. Anserine bursitis is thought to be more common in middle-aged women, but there is no evidence to substantiate this.

Pathology and pathophysiology

Varying degrees of inflammation occur in bursitis.  Synovial cells increase in thickness and may undergo villous hyperplasia.  Over time, granulation tissue and fibrous tissue forms.  An inflammatory reaction occurs, and the bursa becomes filled with fluid.  The fluid is usually rich in fibrin, but can be hemorrhagic.  

Bursitis can occur in stages: acute, recurrent, and chronic.  In the acute stage, local inflammation occurs and the synovial fluid is thickened.  Chronic bursitis can lead to continued pain and eventual disruption and weakening of overlying tendons and ligaments.

Repetitive injury within the bursa causes local vasodilation and increased vascular permeability, which can stimulate the inflammatory cascade.

Differential diagnosis

The differential diagnosis of knee bursitis includes the following:

  • Ligamentous injury
  • Osteoarthritis
  • Septic versus inflammatory bursitis

Distinguishing features include a history of trauma, frequent and sustained pressure, and risk factors such as frequent falls, participation in certain sports, obesity, osteoarthritis, and an impaired immune system.  The physical examination can help to distinguish a bursitis by the location of the pain and swelling, inflammatory signs (erythema, warmth), range of motion of the joint, and observance of gait. X-rays are not usually necessary but can help distinguish other causes of pain such as osteoarthritis.  Bursal fluid aspiration and analysis can help distinguish septic and inflammatory bursitis from non-inflammatory bursitis.

Etiology

Bursitis has many causes:

  • Autoimmune disorders
  • Crystal deposition diseases
  • Infectious diseases
  • Trauma
  • Hemorrhagic disorders
  • Overuse injury

Bursitis and other soft-tissue disorders can also be associated with generalized hypermobility.  Examples of some autoimmune disorders associated with bursitis include rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, and systemic lupus.

Radiographic and laboratory findings

Plain X-rays of the knee are not necessary to make the diagnosis of prepatellar bursitis, infrapatellar bursitis, or anserine bursitis.  They may be useful, however, to identify osteoarthritis (which may be a risk factor for pes anserine bursitis), and to distinguish from other autoimmune inflammatory conditions.  X-ray may be useful to evaluate trochanteric bursitis to detect abnormalities in leg-length, diseases affecting the sacroiliac joints, and structural back disease.  MRI has been utilized to detect bursitis only in cases of suspected underlying conditions. 

Musculoskeletal ultrasound (Figures 1-3) is emerging as a viable imaging modality to assess the knee joint.  Advantages include its ease of availability, economic savings compared to MRI, ability to easily compare abnormalities to the contralateral side, demonstration of fibrillar microanatomy of tendons, ligaments, and muscles, and the ability to compress and dynamically assess structures.  Musculoskeletal ultrasound can be utilized to distinguish difficult cases of joint effusion from that of bursal swelling. 


Figure 1. Musculoskeletal ultrasound of prepatellar bursitis (image courtesy of Dr. David Feinstein)


Figure 2. Musculoskeletal ultrasound of superficial infrapatellar bursitis (image courtesy of Dr. David Feinstein)


Figure 3. Musculoskeletal ultrasound of deep infrapatellar bursitis (image courtesy of Dr. David Feinstein)

Risk factors and prevention

Common risk factors for knee bursitis include excessive kneeling.  Carpet layers, plumbers, and gardeners, for example, may be at increased risk of knee bursitis.  Disturbances in gait cause a vast majority of trochanteric bursitis. 

Steps taken to avoid knee bursitis or prevent its recurrence include wearing kneepads, taking breaks from any repetitive activities, and avoiding excessive squatting.  Steps to avoid hip bursitis also include avoidance of repetitive bending of the hip and direct pressure over the hip.  Overall, the patient needs to rest and cushion and protect the area.

Treatment options

Standard treatment of bursitis includes aspiration and drainage of the bursa if possible.  Depending on the area of involvement, application of a compression dressing after aspiration and avoidance of direct pressure are recommended.  A prescription for a nonsteroidal anti-inflammatory drug (NSAID) to reduce pain and inflammation is recommended for those patients who can tolerate the drugs.  Corticosteroid injections can be considered in the right clinical setting.  Ice is beneficial in acute inflammation.

In cases of trochanteric bursitis, heat treatments and passive stretching exercises can be beneficial. Correcting any leg-length discrepancies or other causes of gait disturbances are also important, in conjunction with restriction of repetitive bending, avoidance of direct pressure, and use of NSAIDs.

Outcomes

Most cases of bursitis will resolve spontaneously or respond to simple aspiration.  Others require corticosteroid injections.  Corticosteroids usually cause a rapid decrease in inflammation, but patients may experience pain and swelling from the injection for a few days.  If symptoms persist and have failed to respond to conservative therapy, then patients are referred for bursectomy where anatomically appropriate.  Physical therapy may be appropriate to help the patient learn exercises to improve flexibility and strengthen muscles.

Holistic medicine

Nonpharmacologic interventions (ice, heat, rest) are safe and may help acutely with pain. Chiropractic medicine, acupuncture, yoga, and osteopathy (aligning the spine, correcting posture, and mobilizing joints) have been noted to have potential usefulness in treating bursitis.  Increasing vitamins A and C and avoidance of caffeine may be beneficial.  

Miscellany

  • Prepatellar bursitis is commonly known as housemaid’s knee.  Housemaids would injure this bursa due to frequent kneeling when cleaning.
  • Infrapatellar bursitis is commonly known as clergyman’s knee.  Clergyman injured this bursa by commonly kneeling on hard surfaces while in prayer.

Key terms

Knee pain, hip pain, bursitis

Skills and competencies

  • Students must take a careful history and be able to distinguish articular from extra-articular joint manifestations


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