A 38-year-old, female retail associate presents to the primary care office with a chief complaint of severe right hip pain and swelling. The patient notes that the pain occurred suddenly the night before, shortly after she ate dinner. She says the hip pain grew progressively worse and the patient was unable to sleep through the night. She also complains of chills and having difficulty walking.



The patient’s past medical history is significant for asthma, which is well controlled with two puffs of Albuterol MDI as needed for shortness of breath and one inhalation of Advair diskus 500/50 twice a day. Her medical history is also positive for non-insulin diabetes mellitus. She takes one tablet of metformin 500 mg twice daily for this condition. Her last glycosolated hemoglobin A1C was 10.0 and was reported one month ago. She admits multiple missed dosages of her diabetic medication in the last two months.

The patient is a single mother of one son. She denies smoking, drinking or illicit drug use. She says she does not exercise. The physical examination reveals a well developed and well nourished woman who appears to waddle as she walks. Her vital signs include a sitting blood pressure of 128/82 and a heart rate of 90 with regular rate and rhythm. Her respiratory rate is 20 breaths per minute and has a temperature of 101.6°. She weighs 167 pounds with clothes. She is 5’6” without shoes.

A physical examination of the hip reveals an erythematous, edematous and tender joint capsule with palpation. The patient also has a painful limitation of motion with flexion-extension and adduction-abduction of the hip.

Diagnostic studies reveal a negative rheumatoid factor, elevation of the erythrocyte sedimentation rate and C-reactive protein, radiographic evidence of soft tissue swelling, joint space widening and displacement of tissue planes by the distended capsule. The synovial fluid is turbid. She also has elevated levels of total protein and lactate dehydrogenase, and the glucose level is depressed.

Which of the following is the most likely diagnosis?
A. Bursitis
B. Monarticular rheumatoid arthritis
C. Acute gout
D. Nongonococcal septic arthritis

Key Insights On The Differential Diagnosis

A. Bursitis is not the correct answer. Inflammation of the bursa occurs as a consequence of trauma or due to the spread of an inflammatory process. Focal pain with tenderness develops over the bursa. One will note trochanteric bursitis on the lateral aspect of the hip, posterior to the trochanter. The clinician will also note increased pain via direct pressure of the greater trochanter or hip flexion and internal rotation. This pain may become worse at night and radiate down the leg to the knee. Bursitis may occur in runners who jog on uneven surfaces and those with one leg slightly shorter than the other.

Gram-negative Enterobacteriaceae also cause septic arthritis, particularly among immunocompromised patients, the chronically ill and intravenous drug abusers.

When patients have an acute inflammatory arthropathy, radiographs often show little more than soft tissue swelling. Treatment consists of preventing the aggravating situation and resting the involved part. One may also administer nonsteroidal antiinflammatory drugs (NSAIDs) or a local glucocorticoid injection.

B. Monoarticular rheumatoid arthritis is not the correct answer. Rheumatoid arthritis typically presents in a subacute fashion with symmetric polyarthritis although atypical forms include monoarticular and asymmetric disease. While a symmetrical pattern of joint involvement is more typical, one may see an asymmetrical pattern in a few patients. While the most common sites are the wrists, proximal interphalangeal (PIP) joints and metacarpophalangeal (MCP) joints, the elbows, neck, hips, knees, ankles and feet may also be involved.

Fatigue may dominate the early clinical presentation and precede the onset of joint symptoms. Other systemic symptoms (fever, weight loss) are prominent in severe cases. Women are more affected than men. Clinicians will find rheumatoid factor (RF) in approximately 75 percent of these cases and this is associated with skin nodules and more aggressive articular and extraarticular disease.

Clinically, synovial inflammation causes swelling, tenderness and limitation of motion. Warmth is usually evident upon examination, especially when it comes to large joints. However, erythema is uncommon. The joint swelling results from the accumulation of synovial fluid, hypertrophy of the synovium and thickening of the joint capsule.

Radiographic evaluation reveals only that which is apparent from physical examination. Essentially, there is evidence of soft tissue swelling and joint effusion. Juxtaarticular osteopenia may become apparent within weeks of onset. Loss of articular cartilage and bone erosions develop after months of sustained activity.

C. Acute gout is not the correct answer. Gout is a common cause of acute monoarticular arthritis. The condition occurs most commonly among middle-aged and older men. Acute gout has a rapid onset, peaking within 12 to 24 hours. The metatarsophalangeal joint of the great toe is the classic site but one may see this in the midfoot, ankles, knees, wrists and olecranon bursae.

Mr. Joseph Krolikowski is a physician assistant and an instructor within the Drexel Hahnemann Physician Assistant Program at Drexel University.

These patients will have sodium urate crystals in the joint fluid and elevated synovial fluid cell counts ranging from 2,000 to 60,000/uL. Effusions appear cloudy due to leukocytes and large amounts of crystals occasionally produce a thick pasty or chalky joint fluid. Although the likelihood of a gouty attack increases with serum uric acid levels, uric acid levels are not diagnostically helpful unless they are extremely high. Alcoholic binges or the new use of thiazide diuretics may precipitate gouty attacks. Patients may even have a mild fever. A rapid response to colchicines helps differentiate crystal-induced arthritis from infection.

D. Nongonococcal septic arthritis is the correct answer. The arthritis of sepsis derives predominantly from hematogenous seeding of the synovium. Occasionally, it is caused by direct extension from a site of trauma or by osteomyelitis. More than 80 percent of cases are monoarticular with gram-positive organisms.

Staphylococcus aureus is the dominant cause, accounting for 60 percent of infectious cases with the majority being methicillin resistant Staph aureus (MRSA). Streptococcus species account for about 18 percent of nongonococcal septic arthritis cases. Gram-negative Enterobacteriaceae also cause septic arthritis, particularly among intravenous drug abusers, immunocompromised patients and the chronically ill.

Joint sepsis is more likely in patients with altered host defenses (diabetes, cirrhosis, immunodeficiency), previously damaged joints (rheumatoid arthritis) or prosthetic joints. Fever, chills and joint inflammation are usually prominent. However, the presentation may be devoid of systemic symptoms, especially if the patient is debilitated or immunosuppressed. In these cases, it is more likely that a larger joint, such as a knee or hip, is involved.

Articular destruction can be rapid. Within 10 days of nongonococcal infection, radiographic evidence of cartilaginous and bony damage may appear.

While cellulitis, bursitis and acute osteomyelitis may produce a similar clinical picture, one should be able to distinguish septic arthritis from these conditions by their greater range of motion and less than circumferential swelling.

Pertinent Treatment Pointers

Treatment of nongonococcal septic arthritis requires prompt administration of systemic antibiotics and drainage of the involved joint. After obtaining samples of synovial fluid for culture, clinicians should proceed with empiric antibiotics directed against the bacteria visualized on smears or against the likely pathogens, given the patient’s age and risk factors.

Dr. Patrick Auth is a physician assistant and is the Director of the Drexel Hahnemann Physician Assistant Program at Drexel University in Philadelphia.

Initial therapy should consist of intravenous bactericidal agents. An intravenous third-generation cephalosporin such as cefotaxime will provide coverage for most community-acquired infections. One may use intravenous oxacillin or nafcillin for gram-positive cocci on the smear, and intravenous vancomycin for MRSA. In addition, clinicians may give an aminoglycoside to intravenous drug users or other patients when Pseudomonas aeruginosa may be the causative agent.

Timely drainage of pus and necrotic debris from the infected joint is required for a favorable outcome. When it comes to septic arthritis of the hip, it is best to manage this condition with an arthrotomy. This is particularly the case when treating young children as an infection can threaten the viability of the femoral head.
These patients should avoid weightbearing until the signs of inflammation have subsided. However, frequent passive motion of the joint is indicated to maintain full mobility.