Nongonococcal septic arthritis.

Gonococcal septic arthritis.

Crystalline-related arthritis (gout, pseudogout).

Inflammatory synovitis [rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriatic arthritis, reactive arthritis (ReA), colitic arthritis].

Hemarthrosis due to hemophilia or anticoagulation.

Osteoarthritis.

Does the patient have any systemic signs or symptoms suggestive of infection? Fevers, chills, or night sweats may indicate a septic arthritis with bacteremia. Possible risk factors for infection should be investigated, such as skin lesions, immunosuppressive therapy, comorbid disease such as diabetes, prior joint damage, and iatrogenic sources such as cortisone injections or surgery.

Does the patient have a history of gout or pseudogout [calcium pyrophosphate disease (CPPD)]? Although gouty flares typically localize to the great toe, crystalline deposition in the larger articular joints may lead to acute, symptomatic effusions. A history of podagra may suggest an inflammatory effusion due to crystalline arthropathy.

Does the patient have a recent history of overuse of the joint? Although the patient may not recall a traumatic incident, joints with underlying arthritis may develop an effusion after minimal overuse. For example, a previously asymptomatic arthritic knee may develop an effusion overnight after a tennis match.

Does the patient have any signs or symptoms of a gonococcal infection; is the patient in the at-risk population? A history of dysuria or urethral discharge may suggest a gonorrheal infection; patients younger than 30 are at greatest risk.

Is there a history of inflammatory arthritis? RA, SLE, and spondyloarthropathies may periodically flare and cause joint effusions.

Is there a history of hemophilic arthropathy? Typically, there is a target joint that may experience bleeding despite periodic infusion of clotting factors. Patients on anticoagulants are at risk of bleeding with less than severe trauma.

Some joints are more accessible to palpation than others; the knee and elbow lend themselves to direct palpation of an effusion, whereas the hip does not. An assessment of the amount of fluid can be performed by milking (i.e., pushing or shifting) the fluid from one area of the joint to another. Joint effusions are subjectively graded as 1+ (small), 2+ (moderate), and 3+ (large). A septic arthritis will usually have a large, 3+ effusion.

Inspection and palpation of the joint may reveal warmth and tenderness. A palpable warmth in the joint indicates either an inflammatory or septic arthritis; a degenerative joint with a reactive effusion will not be noticeably warmer than the surrounding skin. Generally, a septic joint will be diffusely tender to palpation, whereas a reactive effusion due to osteoarthritis will not. Hemarthrosis can be warm due to the pyrogenic effect of the blood.

The joint is typically held in such a way as to maximize volume. The knee and hip are held in slight flexion so as to decrease painful capsular stretch. Weight-bearing joints may have pain with ambulation. Intra-articular pain is present with both active and passive range of motion. The range of motion may be limited due to the effusion. A degenerative joint with effusion will have the sensation of limitation at the extremes of motion whereas a patient with a septic effusion may guard against examination, holding the joint rigidly to avoid motion.

White blood cell (WBC) with differential. A septic arthritis with transient bacteremia may lead to an elevation of the WBC with a left shift. It must be emphasized that a normal WBC does not rule out the possibility of septic arthritis.

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). These nonspecific acute phase reactants will be elevated in inflammatory and septic arthritis. An ESR greater than 25 mm suggests an inflammatory etiology. The higher the ESR and CRP, especially when associated with fever, the greater the likelihood of infection.

Radiologic studies may demonstrate asymmetric narrowing of the articular surfaces in degenerative disease or symmetric narrowing in inflammatory arthritis. Chondrocalcinosis, or deposition of calcium in the articular cartilage or fibrocartilage, is strongly suggestive of CPPD. However, 20% of elderly patients have such deposits and never have an episode of joint inflammation.

Joint aspiration (see Chapter 8). This is the most important of all the laboratory investigations. A joint aspirate should be analyzed for its gross and microscopic appearance, and for microbiologic evaluation. The gross appearance of a reactive, noninflammatory effusion is typically of clear, yellowish, synovial fluid. An inflammatory effusion may be turbid, owing to the relative increase in cellularity. A septic arthritis will range from turbid to grossly purulent.

A cell count with differential of the aspirated fluid should be obtained. A WBC greater than 1,000/mm³ is suggestive of an inflammatory effusion; if WBC is greater than 50,000/mm³, presence of a septic arthritis is of prime concern. Additionally, the differential will reveal a relative neutrophilia, with polymorphonuclear neutrophils (PMNs) greater than 80% of the cells. Microscopic analysis should focus upon the identification of bacteria on Gram staining; also, for the presence of crystals within the PMNs. A diagnosis of gout is made by the presence of negatively birefringent, needle-shaped crystals; CPPD is confirmed by visualizing positively birefringent, rhomboid-shaped crystals in PMNs.

It must be kept in mind that infectious arthritis can “strip” gout and/or pseudogout crystals off the wall of a joint. So, the finding of crystals does not provide assurance that an infection does not exist. The higher the fever and the peripheral white count, the greater is the concern about infection.

Microbiologic analysis should also be done when there is a suspected infectious etiology. A sample of fluid for aerobic and anaerobic cultures may reveal bacterial growth in 48 to 72 hours if septic arthritis is present. Although white cell counts generally can be a guide to the likely diagnosis, infectious arthritis can only be defined by Gram stain and culture.

Once infection has been ruled out, one can choose from among the many therapeutic options, guided by the cause and comorbidities.

An inflammatory effusion may respond to a short course of oral anti-inflammatory medication. The patient should also avoid inciting further synovitis, by resting the joint. A gently compressive ace bandage may help prevent reaccumulation of the effusion. If the synovitis is severe or recurrent, intra-articular steroid injections can be quite helpful.

If uric acid crystals are identified within the synovial fluid, then gout is the presumptive diagnosis. Patients may be treated with indomethacin or alternative anti-inflammatory medication. Institution of allopurinol may help prevent future recurrences, but should never be started in the presence of active joint inflammation and without colchicine coverage.

A clear, reactive effusion in the presence of pre-existing degenerative joint disease may be managed by drainage of the fluid. Patients will usually get symptomatic relief with the initial aspiration of fluid. A gently compressive bandage and avoidance of additional overuse will help prevent recurrence. Intra-articular steroid injections can be quite helpful.

A septic arthritis, supported by a “septic clinical picture” or a WBC greater than 50,000/mm³ in the synovial fluid and a definitive diagnosis by a positive Gram stain and positive microbiologic cultures, requires emergency attention. Time is of the essence because articular cartilage is immediately at risk of permanent damage (see Chapter 46).

The main thrust of treatment, along with optimal antibiotic coverage, is joint drainage. Studies have shown that, in most situations, similar results are obtained from both surgery and daily or twice daily closed needle drainage. However, in the face of persistently positive synovial fluid cultures despite the use of specific antibiotics, lack of clinical improvement, hip infections, or the presence of an aggressive organism such as Staphylococcus aureus or gram-negative rods, orthopedic consultation is appropriate and arthroscopic surgery is indicated and quite effective in improving the short- and long-term outcome.

If the patient is medically stable for surgery, and the above poor prognostic signs exist, a surgical consultation should be obtained from an orthopedic surgeon. Irrigation and debridement of the joint should be performed expeditiously to prevent the destruction of articular cartilage and the onset of osteomyelitis. The irrigation and debridement of the joint may be performed arthroscopically or open, along with continued administration of intravenous antibiotics.

A joint effusion caused by gonococcal infection will typically respond to appropriate antimicrobial medication and will not require surgical intervention. Daily aspirations of the joint effusion can help symptomatically by removing inflammatory mediators.

Fractures (e.g., tibial plateau fractures and tibial eminence avulsions).

Ligamentous rupture (e.g., anterior cruciate ligament or posterior cruciate ligament tears of the knee).

Ligamentous sprain (e.g., medial collateral or lateral collateral ligament sprain).

Fibrocartilage tear (e.g., labral tear of the hip or shoulder; meniscal tears of the knee).

Articular contusion.

How did the injury occur? A detailed description of the injury mechanism can give clues to the diagnosis. For example, a blow to the side of the knee suggests an injury to the medial collateral ligament, and possibly an anterior cruciate ligament tear. Hyperflexion of the hip can cause a labral tear.

Did the patient hear or feel a crack or a pop at the time of injury? Often complete ligamentous ruptures are associated with a distinct sensation of a “pop.”

Was the patient able to bear weight after the injury? The inability to comfortably bear weight suggests the possibility of a fracture in the hip or tibial plateau.

Does the patient feel any clicking within the joint? Mechanical symptoms such as clicking suggest a fibrocartilage tear. Knee meniscal tears can cause clicking when doing pivoting-type activity or with hyperflexion.

Has the patient experienced joint locking? True locking of a joint, defined as the inability to actively move the joint for a certain period of time, indicates that there is something interposed between the articular surfaces, such as a loose body. Patients can usually shake the joint or passively move it to unlock the joint.

The joint should be palpated for any obvious tenderness, which may indicate areas of contusion, sprains, or occult fractures. The ligament examination should not only check for the competency of the ligaments, but also whether or not pain is elicited. Pain, without any compromise of ligamentous competency, indicates a sprain; pain and failure of ligamentous competency indicates a rupture.

Motion should be assessed as to whether certain joint positions elicit pain. Rotatory motions of the knee that cause pain may indicate a meniscal tear; pain with hyperflexion and adduction of the hip may indicate a labral tear.

Joint aspiration may provide additional information about the type of injury. A hemarthrosis with fat droplets indicates a fracture of bone. The fracture may be a periarticular fracture or an avulsion fracture of ligamentous attachments.

X-ray analysis in two planes can help identify periarticular fractures.

Magnetic resonance imaging (MRI) is the best imaging modality to look at the soft tissues inside and surrounding the joint.

Immediate management includes RICE: rest, ice, compression, and elevation. This algorithm should be followed for at least 48 to 72 hours.

Joint aspiration may provide symptomatic relief, but is not necessary. Fluid will usually reaccumulate despite attempts to keep it down.

Splinting may take the stresses off the injured area. Many traumatic injuries of the knee are managed with a hinged knee brace (knee immobilizer), which alleviates stresses on the collateral and cruciate ligaments.

A sling may help relieve the stresses on the elbow and shoulder by supporting the weight of the arm against gravity.

If the patient has pain with ambulation, protected weight bearing may help unload the stresses upon that joint. A cane, crutches, or a walker can be used depending on the age of the patient and the amount of pain.

If a sprain is diagnosed, once the acute swelling has subsided, a physical therapy program can help regain range of motion.

In the case of a hemarthrosis, the inability to bear weight, ligamentous laxity, or swelling that does not improve, referral to an orthopedic surgeon is indicated to determine whether or not surgery is required.

A short course of nonsteroidal anti-inflammatory drugs (NSAIDs) is helpful to treat pain and inflammation.

Orthopedic consultation is appropriate in setting a likely fracture or significant joint or ligamentous damage.

Hip fracture/occult hip fracture.

Stress fracture of the femoral neck.

Stress fracture of the tibial shaft or plateau.

Insufficiency fracture of the sacrum with or without a pubic ramus fracture.

Compression fracture of the thoracolumbar spine.

Exacerbation of existing osteoarthritis.

Exacerbation of RA or other systemic inflammatory disorders.

Femoral head collapse in the setting of osteonecrosis.

Acute lumbosacral sprain with or without radiculopathy.

Vascular occlusion.

Over what time period has this condition evolved? An insidious onset suggests a gradual mechanical failure brought on by repetitive activity (a stress fracture). An acute onset preceded by a traumatic event suggests a fracture.

Has the patient adopted any new activity recently? An increase in the activity level of the patient beyond the body’s ability to adapt can lead to a stress fracture. An example is marathon training leading to stress fractures in the metatarsals, tibial shaft, or femoral neck.

Is there a history of osteoporosis? Osteoporotic bone can succumb to relatively minor loads; a vertebral body compression fracture can occur with lifting of grocery bags or with a cough.

Is there a history of hip osteoarthritis? With pre-existing osteoporosis and degenerative joint disease of the hip, subchondral fractures of the femoral head may occur, leading to rapidly progressive osteoarthritis, and difficulty in bearing weight. RA or other inflammatory disorders rarely lead to total inability to walk. If that is the case or if walking ability is severely limited, either a very severe joint disease with superimposed secondary osteoarthritis or a superimposed infection, fracture, and mechanical joint problem must be considered.

Is there a history of steroid use, alcohol abuse or diseases such as sickle cell disease or Gaucher’s disease that could lead to osteonecrosis? Does the patient have systemic lupus, with or without a history of steroid therapy?

Does the patient have a history of vascular disease such as angina, myocardial infarction, or peripheral vascular disease with claudication?

The patient should be observed while attempting to walk. A decreased stance phase with a shortened stride length is the definition of an antalgic gait due to joint pain. Asking the patient to localize the pain while ambulating will help the physician focus on the correct area.

All weight-bearing joints (tarsal, ankle, knee, hips, and sacroiliac) should be inspected for tenderness, swelling, and range of motion. Point tenderness over a bone may indicate a stress fracture. Active straight leg raising in the supine position increases joint reactive forces across the hip. Pain while straight leg raising is a localizing finding suggesting hip pathology such as an occult fracture. Internal rotation of the hip is the most sensitive position to bring out hip pathology, be it fracture or arthritis.

The spine, including the sacrum, should be palpated over the spinous processes and paraspinal musculature. Point tenderness over the spinous processes may suggest a compression fracture, whereas tenderness in the paraspinal musculature may indicate a sprain. A careful neurovascular examination is a requisite to evaluate neurologic deficit caused by compression fractures.

Because the back can be the origin of pain that “presents” all along the sciatic nerve distribution in the lower extremity, examination of the back is important as is a neurologic examination that includes testing of reflexes and muscle strength.

Vascular occlusion can lead to severe leg pains and therefore an examination of leg pulses is mandatory.

Plain radiographs are quite helpful in defining the presence of joint damage due to RA or osteoarthritis. A fracture can be missed either because the reactive bone changes may not occur for 1 to 2 weeks, or the patient could be osteopenic and the fracture line may not be obvious. Osteonecrosis may not be seen at all with this imaging technique and requires assessment with a bone scan or MRI.

Radiographs in two planes can help identify whether or not a fracture is the cause. A chronic stress fracture may appear as sclerosis, but often radiographs are unrevealing.

Nuclear medicine studies, such as a Technetium 99 three-phase bone scan, will demonstrate areas of increased bone turnover. A bone scan is helpful especially when the physical examination was not able to localize the problem. The caveat is that an occult fracture occurring after trauma will not show up on the bone scan until 48 hours have elapsed. A sacral insufficiency fracture will show up as an “H pattern” on the bone scan.

Computed tomography (CT) scan of the region of interest can demonstrate occult fractures of the hip, tibial shaft, and tibial plateau. Three-dimensional reconstructions may be necessary to visualize the fracture lines.

MRI of the region of interest can similarly evaluate for occult and stress fractures. MRI has the added benefit of imaging bone edema patterns and avoiding the use of ionizing radiation.

The affected area should immediately be protected from weight bearing by the use of crutches or a walker, depending upon the age and physical condition of the patient.

Stress fractures of all types, especially if the trauma that led to it was minimal (this is called a fragility fracture), should stimulate an evaluation for osteopenia/ osteoporosis and possible treatment for it. This includes a dual energy x-ray absorptiometry (DEXA) and a search for the cause (see Chapter 53).