Patients may report "joint" pain regardless of whether the cause involves the joint itself or surrounding (periarticular) structures such as tendons and bursae; in both cases, pain in or around a single joint will be referred to as monoarticular pain.
Pain originating within a joint (arthralgia) may be caused by joint inflammation (arthritis). Inflammation tends to result in accumulation of intra-articular fluid (effusion) and clinical findings of warmth, swelling, and uncommonly erythema. With effusion, prompt assessment is essential to exclude infection.
Acute monoarticular pain is sometimes caused by a disorder that characteristically causes polyarticular pain (eg, rheumatoid arthritis) and thus may be the initial manifestation of a polyarthritis (eg, psoriatic arthritis, rheumatoid arthritis—see Pain in Multiple Joints).
Pathophysiology of Pain in a Single Joint
Pain in and around a joint may involve
Inflammation (due to, eg, infection, crystal-induced arthritis, or autoimmune systemic inflammatory disorders)
Noninflammatory problems, usually mechanical (eg, trauma, internal derangements)
The synovium and joint capsule are major sources of intra-articular pain. The synovial membrane is the main site affected by inflammation (synovitis). Pain that originates from the menisci is more likely to be a result of injury.
Etiology of Pain in a Single Joint
The most common causes of acute monoarticular pain overall are the following:
Injury
Infection
Crystal-induced arthritis
With injury, a history of trauma is usually present and suggestive. Injury can affect intra-articular and/or periarticular structures and involve direct injury (eg, twisting during a fall) or overuse (eg, repetitive motion, prolonged kneeling).
Infection most often involves the joint (septic arthritis), but periarticular structures, including bursae, overlying skin, and adjacent bone, also may become infected.
Among young adults, the most common causes are the following:
Injury (most common)
Infection
Primary inflammatory disorders (eg, gout)
Among older adults, the most common nontraumatic causes are the following:
Osteoarthritis (most common)
Crystal-induced arthritis (usually gout or calcium pyrophosphate arthritis [previously called pseudogout])
The most dangerous cause of joint pain at any age is acute infectious (septic) arthritis. Prompt drainage, IV antibiotics, and sometimes operative joint lavage may be required to minimize permanent joint damage and prevent sepsis and death.
Rarer causes of monoarticular pain include osteonecrosis, pigmented villonodular synovitis, hemarthrosis (eg, in hemophilia or coagulopathies), tumors (see table Some Causes of Pain in and Around a Single Joint), and disorders that usually cause polyarticular pain, such as reactive arthritis and enteropathic arthritis.
The most common cause of periarticular pain is injury, including overuse. Common periarticular disorders include bursitis and tendinitis; epicondylitis (eg, lateral epicondylitis), fasciitis, and tenosynovitis can also develop. Periarticular infection is less common.
Sometimes, pain is referred to a joint. For example, a splenic injury may cause left shoulder pain, and children with a hip disorder may complain of knee pain.
Some Causes of Pain in and Around a Single Joint
Cause | Suggestive Findings | Diagnosis* |
|---|---|---|
Crystal-induced arthritis, usually caused by uric acid crystals (gout) or calcium pyrophosphate crystals (calcium pyrophosphate arthritis) and sometimes by calcium hydroxyapatite crystals | Acute, self-limited, recurrent episodes of monarthritis, most often in the first metatarsophalangeal joint, ankle, or knee (gout) or wrist or knee (calcium pyrophosphate arthritis) Sometimes visible gouty tophi (usually on periarticular structures) | Arthrocentesis with examination for crystals Sometimes ultrasound Sometimes dual energy CT scan Sometimes x-rays for transient hydroxyapatite deposition causing calcific periarthritis |
Hemarthrosis | Acute pain and effusion spontaneously or after trauma Typically, a known bleeding disorder | Arthrocentesis |
Infectious (septic) arthritis (eg, bacterial, fungal, viral, mycobacterial, spirochetal) | Acute or subacute onset of pain, swelling, and warmth, commonly with decreased range of motion More frequent in immunosuppressed patients, IV drug users, patients with diabetes or prior antibiotic use, and patients with risk factors for sexually transmitted infections | Arthrocentesis with cell counts, Gram stain, and cultures |
Monarticular or oligoarticular arthritis in later stage of Lyme disease Prior manifestations of Lyme disease, such as erythema migrans, fever, malaise, and/or myalgias following a tick bite in an endemic area | Serologic testing for antibodies against Borrelia burgdorferi | |
Chronic indolent pain with or without swelling, usually in older adults Bony hypertrophy Sometimes obesity, history of joint overuse (eg, in professional athletes), and/or bony enlargement | X-ray | |
Osteomyelitis adjacent to a joint (uncommon) | Fever and poorly localized pain without joint swelling or erythema | X-ray plus bone scan, CT, or MRI Bone biopsy with culture |
Osteonecrosis (avascular necrosis) | Often past or current corticosteroid use or sickle cell disease | X-ray Usually MRI |
Periarticular disorders (eg, bursitis, epicondylitis, fasciitis, tendinitis, tenosynovitis) | Pain with active joint movement; minimal pain with passive movement and joint compression Point tenderness and sometimes swelling and/or erythema over the bursa, tendon insertion site, or other periarticular structure (eg, fascia); minimal localized tenderness over joint, no effusion | Clinical evaluation Sometimes aspiration of bursal fluid for Gram stain, cell count, crystal analysis, and culture |
Psoriatic arthritis (causes oligoarticular or polyarticular pain more often than monoarticular pain) | Usually large joint effusion in the painful joint, often in a patient with psoriasis May occur with dactylitis or enthesitis | Clinical evaluation X-ray |
Trauma (eg, sprain, meniscal tear, fracture) | Onset following significant and usually recent trauma | X-ray Sometimes MRI (eg, if x-ray normal) and/or arthroscopy |
Insidious, slowly progressive, and eventually constant pain, usually with joint swelling | X-ray MRI | |
* Patients with joint effusion or inflammation should have arthrocentesis (with cell counts, Gram stain, cultures, and crystal examination), and usually erythrocyte sedimentation rate (ESR) and C-reactive protein. X-rays are often unnecessary. | ||
Evaluation of Pain in a Single Joint
Acute monoarticular joint pain requires rapid diagnosis because infectious (septic) arthritis requires rapid treatment.
Clinical evaluation should determine whether the joint or periarticular structures are the cause of symptoms and whether there is joint inflammation. If signs of inflammation are present or the diagnosis is unclear, symptoms and signs of polyarticular and systemic disorders should be sought.
History
History of present illness should focus on the location of pain, acuity of onset (eg, abrupt, gradual), whether the problem is new or recurrent, and whether other joints have caused pain in the past. Also, temporal patterns (eg, persistent vs intermittent), associated symptoms (eg, swelling), exacerbating and mitigating factors (eg, activity), and any recent or past trauma to the joint should be noted. Patients should also be asked about unprotected sexual contact (indicating risk of sexually transmitted diseases), previous Lyme disease, and possible tick bites in areas where Lyme disease is endemic.
Review of systems may provide clues to systemic disorders. Review of systems should seek extra-articular symptoms of causative disorders, including fever (infection, sometimes crystal-induced arthritis), urethritis (gonococcal arthritis or reactive arthritis), rash or eye redness (reactive arthritis, spondylitis, vasculitis, or psoriatic arthritis), history of abdominal pain and diarrhea (inflammatory bowel disease), and recent diarrhea or genital lesions (reactive arthritis).
Past medical history is most likely to be helpful if pain is chronic or recurrent. Past medical history should identify known joint disorders (particularly gout and osteoarthritis), conditions that may cause or predispose to monoarticular joint pain (eg, bleeding disorder, bursitis, tendinitis), and disorders that can predispose to a joint disorder (eg, sickle cell disease or chronic corticosteroid use predisposing to osteonecrosis). Drug history should be reviewed, particularly for use of anticoagulants, quinolone antibiotics (tendinitis), or diuretics (gout). A family history should also be obtained (some spondyloarthropathies).
Physical examination
A complete physical examination is done. All major organ systems (eg, skin and nails, eyes, genitals, mucosal surfaces, heart, lungs, abdomen, nose, neck, lymph nodes, neurologic system) should be examined, as well as the musculoskeletal system. Vital signs are reviewed for fever. Examination of the head, neck, and skin should note any signs of conjunctivitis, psoriatic plaques, tophi, or ecchymoses. Genital examination should note any discharge or other findings suggesting sexually transmitted infections.
Because involvement of other joints can be clues to a polyarthritis and a systemic disorder, all joints should be inspected for tenderness, deformities, erythema, and swelling.
Palpation helps determine the location of tenderness. Palpation also helps detect joint effusion, warmth, and bony hypertrophy. The joint can also be compressed without flexing or extending it. Range of motion is assessed actively and passively, with attention to the presence of crepitus and whether pain is triggered by joint motion (passive as well as active). For injuries, the joint is stressed with various maneuvers (as tolerated) to identify disruption of cartilage or ligaments (eg, in the knee, valgus and varus tests, anterior and posterior drawer tests, Lachman test, McMurray test). Findings should be compared with those in the contralateral unaffected joint to help detect more subtle changes. Noting whether the tenderness is directly over the joint line or adjacent to it or elsewhere is particularly helpful in determining whether pain (particularly when the knee is involved) is articular or periarticular.
Large effusions in the knee are typically readily apparent. The examiner can check for minor effusions by pushing the suprapatellar pouch inferiorly and then pressing medially on the lateral side of the patella on an extended knee. This maneuver causes swelling to appear (or be palpable) on the medial side. Large knee effusions in obese patients are best detected with ballottement of the patella. In this technique, the examiner uses both hands to push in toward the center of the knee from all four quadrants and then uses 2 or 3 fingers to push the patella down into the trochlear groove and releases it. Clicking or a feeling that the patella is floating suggests an effusion.
Periarticular structures also should be examined for point tenderness, such as at the insertion of a tendon (enthesitis), over a tendon (tendinitis), or over a bursa (bursitis). With some types of bursitis (eg, olecranon, prepatellar), swelling and sometimes erythema may be localized at the bursa.
Red flags
The following findings are of particular concern:
Erythema, warmth, effusion, joint capsule tenderness, and decreased range of motion
Fever with acute joint pain
Acute joint pain in a sexually active young adult
Skin breaks with signs of cellulitis adjacent to the affected joint
Underlying bleeding disorder or use of anticoagulants
Systemic or extra-articular symptoms
Interpretation of findings
Recent significant trauma suggests that injury is the cause (eg, fracture, meniscal tear, or hemarthrosis). However, trauma does not rule out other causes, and patients often mistakenly attribute newly developed nontraumatic pain to an injury. Testing is often necessary to rule out serious causes and establish the diagnosis.
Acuteness of onset is an important feature. Severe joint pain that develops over hours suggests crystal-induced arthritis or, less often, infectious arthritis. Previous attacks of rapid-onset monarthritis suggest recurrence of crystal-induced arthritis, particularly if that diagnosis had been confirmed previously. Gradual onset of joint pain is more typical of rheumatoid arthritis or noninfectious arthritis. Gradual onset, although uncommon in acute bacterial infectious arthritis, can occur in certain infectious arthritides (eg, mycobacterial, fungal).
Whether pain is intra-articular, periarticular, or both (eg, in gout, which can affect intra- and extra-articular structures) and whether there is inflammation are key determinations, based mainly on physical findings. Pain during rest and on initiating activity suggests joint inflammation, whereas pain worsened by movement and largely relieved by rest suggests mechanical or noninflammatory disorders (eg, osteoarthritis). Pain that is worse with passive as well as active joint motion on examination, and that restricts joint motion, usually indicates inflammation. Increased warmth and erythema also suggest inflammation, but these findings are often insensitive, so their absence does not rule out inflammation.
Pain that worsens with active but not passive motion may indicate tendinitis or bursitis, as can tenderness or swelling localized over a bursa or tendon insertion site. Tenderness or swelling at only one side of a joint, or away from the joint line, suggests an extra-articular origin (eg, tendons or bursae); localized joint line tenderness or more diffuse involvement of the joint suggests an intra-articular cause. Compressing the joint without flexing or extending it is not particularly painful in patients with tendinitis or bursitis but is quite painful in those with arthritis.
Involvement of the first metatarsophalangeal joint (podagra) suggests gout but can also result from infectious arthritis, reactive arthritis, or psoriatic arthritis.
Symptoms indicating dermatologic, cardiac, or pulmonary involvement suggest disorders that are systemic and more commonly result in polyarticular joint pain.
Testing
Joint aspiration (arthrocentesis) for synovial fluid examination should be done in patients with joint effusion (see How to Do Arthrocentesis). Synovial fluid examination includes white blood cell (WBC) count with differential, Gram stain and cultures, and microscopic examination for crystals using polarized light. Finding crystals in synovial fluid confirms crystal-induced arthritis but does not rule out coexisting infection. A noninflammatory synovial fluid (eg, < 1000/mcL [< 1 × 109/L] WBCs) is more suggestive of osteoarthritis or trauma. Hemorrhagic fluid is consistent with hemarthrosis. Synovial fluid WBC counts can be very high (eg, > 50,000/mcL [> 50 × 109/L] WBCs) in both infectious and crystal-induced arthritis. Sometimes, molecular techniques, such as polymerase chain reaction, are used to detect the presence of microorganisms.
For some patients with prior confirmed gouty arthritis, a recurrent episode may not require any testing. However, if infection is a reasonable possibility, or if symptoms do not rapidly resolve after appropriate therapy for gouty arthritis, arthrocentesis should be done.
X-rays rarely change the diagnosis in acute monarthritis unless fracture is suspected. X-rays may reveal signs of joint damage in patients with a long history of recurrent arthritis. Other imaging tests (eg, CT, bone scan, but most often MRI) are rarely necessary acutely but may be indicated for diagnosis of certain specific disorders (eg, osteonecrosis, tumor [see table Some Causes of Pain in and Around a Single Joint], occult fracture, pigmented villonodular synovitis).
Blood tests (eg, erythrocyte sedimentation rate [ESR], rheumatoid factor, anti-cyclic citrullinated peptide [anti-CCP] antibody) may help support a clinically suspected diagnosis of a systemic inflammatory disorder (eg, rheumatoid arthritis) but are not specific. Serum urate level should not be used to diagnose gout because it is neither sensitive nor specific and does not necessarily reflect the presence of intra-articular uric acid deposits.
Treatment of Pain in a Single Joint
Overall treatment is directed at the underlying disorder. IV antibiotics are usually given immediately or as soon as possible if acute bacterial infectious arthritis is suspected.
Physical therapy after the acute symptoms have lessened is useful to increase or maintain range of motion and strengthen adjacent muscles.
Key Points
Arthrocentesis is mandatory to rule out infection in acute monoarticular joint pain with joint effusion.
Infection is the most common cause of acute nontraumatic monarthritis in young adults, whereas osteoarthritis is the most common cause in older adults.
Crystals in synovial fluid confirm crystal-induced arthritis but do not rule out coexisting infection.
Do not use serum urate level to diagnose gout.
Joint pain that is still unexplained after arthrocentesis and x-ray should be evaluated with MRI to rule out uncommon etiologies (eg, occult fracture, osteonecrosis, pigmented villonodular synovitis) and molecular techniques, such as polymerase chain reaction, should be done to detect the presence of microorganisms.
