Disorders of the Knee
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[edit] Disorders of the Knee
Elinor A. Mody
Jerry M. Greene
The knee is one of the most frequently injured joints and the joint most often affected by systemic inflammatory and neoplastic disease.The physician must be familiar with the regional anatomy, especially the bony structures, ligaments, tendons, bursae, and cartilage, to perform a focused physical examination of the knee, to order the appropriate diagnostic tests, and to determine the differential diagnosis of the painful knee.
[edit] ANATOMY
The knee, one of the largest joints in the body, is formed from the femur, tibia, fibula, and patella.The femoral condyles and tibial plateaus create a hinge, capped by the patella within its tendinous mechanism.The cartilaginous medial and lateral menisci cushion the tibial plateaus and femoral condyles and distribute the forces across these areas.The medial and lateral collateral ligaments and the anterior and posterior cruciate ligaments provide stability to the knee.Several bursae are located external to the synovial membrane and capsule of the knee joint (Figure 129-1)
[edit] PATIENT EVALUATION
[edit] History
Important historic features include the temporal course of the knee pain and the nature of onset.Pain tends to be acute in cases of trauma, crystal diseases, sepsis, and hemorrhage.Asubacute or insidious onset is more consistent with a systemic inflammatory disease, tumor, or osteonecrosis.The location, character, radiation, aggravating and relieving factors, severity of the pain, and associated local symptoms (e.g., swelling, stiffness, redness, limitation of motion) are important historic features to elicit.Systemic symptoms (e.g., weight loss, fever, chills, malaise) are also significant.
The hallmarks of inflammatory synovitis are morning stiffness and pain at rest.Pain only during certain activities suggests a mechanical or traumatic disorder.Involvement of other joints should be assessed.In particular, polyarticular involvement of the joints of the wrists, hands, and feet suggests an inflammatory synovitis such as rheumatoid arthritis.Back pain with morning stiffness suggests spondylitis.A review of systems for rash, myalgias, pleuritic chest pain, mucosal lesions, fever, diarrhea, weight loss, neurologic symptoms, and malaise may suggest other etiologies, such as Lyme disease, inflammatory bowel disease, or systemic lupus erythematosus (SLE).
Hyperparathyroidism, hypothyroidism, hemochromatosis, and aging predispose to calcium pyrophosphate arthropathies, and alcohol abuse predisposes to gout.Unprotected sexual activity and intravenous drug use predispose to gonococcal and nongonococcal bacterial arthritis.Medication history is important.For example, diuretic use may contribute to gouty arthritis, and anticoagulation may increase the risk for hemarthrosis.Review of medical problems is important to assess for contraindications to drug therapy, such as peptic ulcer disease or renal disease when considering nonsteroidal antiinflammatory drug (NSAID) therapy.Family history is always important, since several types of arthritis have a heritable component.
[edit] Physical Examination
Inspection of the affected knee should include observation for erythema, ecchymosis, swelling, abrasions, puncture wounds, and active range of motion.The examiner should palpate the joint line, bursae, muscle, tendons, ligaments, and bones in an attempt to localize tenderness.Joint line tenderness may suggest meniscal or ligamentous injury.An effusion may be demonstrated by eliciting a bulge sign(Fig.129-2).As the patient lies supine with knees fully extended and the quadriceps muscle relaxed, the medial aspect of the knee is massaged in a cephalad direction.The lateral aspect of the knee is then stroked inferiorly.An effusion is detected by the resultant bulge sign.Another maneuver to elicit excessive synovial fluid in the knee is to apply rapid, downward pressure on the patella; if a click is felt as the patella touches the femoral condyle, an effusion is probably present.This is also referred to as patellar ballottement. Occasionally, obesity or synovial bogginess (as often present in rheumatoid arthritis) may result in a false-positive ballottement sign.The examiner should also palpate the popliteal space for swelling that may occur with popliteal artery aneurysm, Baker's cysts, and tumors.Passive range of motion of the knee should also be performed.
Several maneuvers may help elicit mechanical disorders. McMurray's test is useful for diagnosing meniscal injury.This is performed by passive flexion of the knee with the patient lying supine.The lower leg is externally rotated at fullflexion, then held in external rotation, and the knee is passively extended.A painful click near the top of the extension arc is a positive finding.The maneuver is then repeated with the lower leg in internal rotation.This tests for both medial and lateral meniscal tears or injury.Simply taking the knee through flexion and extension while feeling and listening for crepitus is also helpful in assessing such mechanical problems as a loose body in the knee joint.In the absence of signs of inflammation, crepitus suggests osteoarthritis.
A general examination may reveal evidence of a systemic disease associated with knee pathology.The nervous system, back, and hip merit particular attention because of possible referred pain to the knee.Cutaneous clues to the cause of arthritis include psoriasis, erythema chronicum migrans, rheumatoid nodules, and tophi.
[edit] LABORATORY TESTS AND DIAGNOSTIC PROCEDURES
Often the first diagnostic test sought after a thorough physical examination is a radiograph, particularly if there is a history of trauma or if a mechanical disorder is suspected.The most useful view is an anteroposterior (AP) film, which allows visualization of the medial and lateral femorotibial compartments of the knee.If fracture is not suspected, weight-bearing AP radiographs most accurately assess narrowing of the cartilage of the femorotibial joint.The skyline, or sunrise, view allows the physician to visualize the patella and the patellar surfaces that contact the femoral condyles.Tunnel views may also help, particularly in assessing ligamentous injuries, osteoarthritis, intraarticular loose bodies, and osteonecrosis.The lateral view is particularly helpful in assessing for effusion in the suprapatellar recess.
Synovial fluid analysis is important in distinguishing noninflammatory conditions from inflammatory joint disease.Arthrocentesis should always be performed under aseptic conditions to prevent infection and to obtain a sterile specimen for bacterial cultures.In immunocompromised patients, fungal and mycobacterial cultures should be sent as well.Another specimen should be sent for white blood cell count (WBC) and differential.If WBC reveals more than 1000/mm3, the fluid is inflammatory.WBC may also reveal evidence of intraarticular bleeding.If the synovial fluid is inflammatory, Gram's stain and culture should be performed to evaluate for joint sepsis.The fluid is examined with polarizing microscopy for birefringent crystals, specifically sodium urate and calcium pyrophosphate.With alizarin red staining of joint fluid smears, hydroxyapatite crystals may be visualized.The presence of fat droplets in synovial fluid suggests fracture of the bone into the marrow space.
Several blood tests may help in evaluation of knee pain.Erythrocyte sedimentation rate is a general screen for inflammatory disorders, as is a complete blood count, particularly WBC and differential.A routine chemistry panel is useful to assess for renal disease because renal insufficiency may affect therapeutic options.Depending on the clinical setting, serum urate level, rheumatoid factor, or antinuclear antibody level may also be helpful.Serum calcium, phosphate, magnesium, alkaline phosphatase, thyroid function, and iron studies should be considered in patients with pseudogout or chondrocalcinosis.
Magnetic resonance imaging (MRI) allows visualization of joint fluid, synovial swelling, ligaments, menisci, cartilage, and bone (including marrow).If infection is suspected and cannot be completely characterized by the routine methods, arthroscopy with synovial biopsy may be considered; this is particularly helpful if fungal or mycobacterial arthritis is suspected.Arthroscopy may also assist in the evaluation and treatment of internal derangements of the knee, such as meniscal tears.
[edit] SELECTED CAUSES OF KNEE PAIN
[edit] Inflammatory Arthritis
Any arthritis causing a purulent effusion is regarded as inflammatory.Although this category includes many different diseases, some general patterns occur; frequently more than one joint is affected, and the conditions tend to be chronic or recurrent.Knee arthritis may be a prominent manifestation of the disease.Inflammatory joint diseases that frequently involve the knee include gout, calcium pyrophosphate arthropathy (pseudogout), rheumatoid arthritis, the spondyloarthropathies(e.g., ankylosing spondylitis, Reiter's syndrome), septic arthritis, Lyme disease, mechanical disorders, and tumors (Table 129-1)
Table 129-1 Selected Causes of Knee Pain
| Disorder | Epidemiology | History | Physical examination | Diagnostic tests | Differential diagnosis | Management |
|---|---|---|---|---|---|---|
| Gout | Middle age, elderly, overproducers of urate, transplant patients | Acute onset of pain, often with previous attack in first MTP | Warmth, erythema, effusion, exquisite tenderness | High synovial WBC, urate crystals seen under polarizing microscope, “rat bite” erosions on radiograph | RA, spondylitis, other crystal-induced arthropathy, infection | NSAIDs, colchicine, local corticosteroid injection (acute), allopurinol or uricosuric (chronic) |
| Pseudogout | Elderly, patients with metabolic disorders, e.g., hypothyroidism, hypomagnesemia, ochronosis, hemochromatosis, Wilson's disease, hyperparathyroidism | Acute onset of pain; if metabolic disease, systemic complaints | Similar to gout | High synovial WBC, calcium pyrophosphate crystals seen under polarizing microscope, chondrocalcinosis on radiograph | Gout, RA, spondylitis, infection | NSAIDs, colchicine, local corticosteroid injection (acute), daily colchicine as prophylaxis against further attacks[1] |
| Rheumatoid arthritis | Age varies, usually female | Morning stiffness, involvement of joints of hand, multiple joint involvement, fatigue, multiple attacks | Warmth, erythema with effusion, “boggy” synovium with longstanding disease, symmetric involvement of joints, decreased ROM | High synovial WBC, RF often positive, elevated ESR, anemia, consistent with chronic disease, bone erosions on radiographs | Crystal-induced arthropathy, spondylitis, infection | NSAIDs, local corticosteroid injection, second-line agents (e.g., methotrexate, gold) |
| Spondyloarthropathy (reactive arthritis,Reiter's syndrome) | Young adults, male predominance; patients with associated disorders, e.g., IBD; psoriasis;Chlamydia, Yersinia, or Shigella infection; ankylosing spondylitis | Acute or subacute onset of pain, often with low back pain; pain in other joints; component of morning stiffness; possible systemic complaints related to underlying condition | Warmth, erythema, with effusion; “boggy” synovium with longstanding disease; evidence of underlying disease (e.g., oral ulcers, rash, nail changes); decreased ROM of spine | High synovial WBC, erosions on radiograph, sacroiliitis on radiograph, squaring of vertebral bodies, syndesmophytes | RA, crystal-induced arthritis, infection | NSAIDs, local corticosteroid injection, sulfasalazine, methotrexate |
| Gonococcal infection | Young adults predominantly, but any age if sexually active | Acute onset of symptoms, may complain of GU symptoms, recent menses, general malaise | Warmth, erythema, with very large tense effusion, decreased ROM, maculopapular rash over trunk, fever, urethral or cervical discharge, arthritis of other joints, tenosynovitis | High synovial WBC, positive culture for gonococci from genitourinary tract, blood, or synovial fluid | RA, spondylitis, crystal-induced arthropathy, nongonococcal infection, Lyme disease | Ceftriaxone, penicillin G for sensitive strains |
| Nongonococcal infection | IV drug abusers, severely debilitated, patients prone to fulminant sepsis or endocarditis | Acute onset of severe pain, swelling, redness, decreased ROM, possible associated systemic symptoms, and arthritis in other joints | Warmth, erythema, effusion, decreased ROM, signs of source for bacteremia (e.g., pneumonia, UTI) | Very high synovial WBC, positive synovial or blood culture or Gram's stain, high ESR, elevated peripheral WBC, periosteal elevation on radiograph suggests concomitant osteomyelitis | RA, spondylitis, crystal-induced arthritis, gonococcal infection | IV antibiotic therapy guided by Gram's stain, culture results, sensitivities; drain with needle aspiration or arthroscopically; ROM exercises; analgesics |
| Lyme disease | Travelers to or residents of endemic areas | Subacute onset of symptoms, swelling, warmth, decreased ROM, pain, history of ECM skin lesion(s), Bell's palsy, other painful joints | Warmth, erythema, effusion, “boggy” synovium with longstanding disease | Lyme titers, synovial fluid culture rarely positive, radiographs may eventually show erosions | RA, spondylitis, gonococcal and other nongonococcal infection, crystal-induced arthropathy | IV penicillin G, ceftriaxone |
| Fracture | Any age, risk factors include steroid use, osteoporosis, metastatic malignancy | History of trauma, sudden onset of pain, swelling, warmth | Swelling, tenderness over affected area, pain on weight bearing, decreased ROM | Bloody synovial fluid, may show fat droplets under polarizing microscopy, fracture seen on radiograph, bone scan may detect stress fractures inapparent on radiograph | Meniscal tear, ligamentous tear, hemophilia, PVNS, anticoagulant therapy | Splinting to protect against additional neurovascular injury, reduction, casting |
| Ligamentous injury | Young adults, athletes | Trauma with pivoting or hyperextension, feeling of “giving way,” acute pain and swelling | Swelling, point tenderness medial or lateral joint line, positive anterior/posterior drawer sign, medial or lateral laxity depending on ligament disrupted | Bloody or serosanguineous noninflammatory synovial fluid, radiographs to rule out fracture, MRI reveals high T2 signal in area of ligamentous tear | Meniscal tear, fracture, hemophilia, PVNS, anticoagulant therapy | Analgesics, knee immobilizer, orthopedic consultation for surgical repair of complete tears in active patients |
| Meniscal tear | Two groups: elderly with OA and young adults, athletes | Acute or subacute onset of pain, locking, painful popping | Swelling, tenderness over the lateral or medial joint line, positive McMurray's test | Bloody or serosanguineous synovial fluid, radiograph to rule out fracture; MRI, arthrography, or arthroscopy diagnostic | Fracture, ligamentous tear, hemophilia, PVNS, anticoagulant therapy, worsening OA | Initial conservative (rest, NSAIDs), if unsuccessful, orthopedic referral for arthroscopic debridement, or total knee replacement if concomitant severe OA |
| Osteonecrosis (AVN) | Any age, patients with sickle cell anemia, chronic steroid use, alcoholism, decompression illness, trauma, SLE, dyslipoproteinemia | Acute onset of pain, swelling, rest pain, increased pain with weight bearing | Swelling, tenderness, decreased ROM | Area of subchondral collapse appears after weeks on plain radiograph, MRI most sensitive for AVN before subchondral collapse | Tumor, fracture osteomyelitis, OA, meniscal tear | Conservative initial (no weight bearing, NSAIDs, analgesics); if unsuccessful, tibial osteotomy, hemiarthroplasty, or total knee replacement |
| Osgood-Schlatter syndrome | Young adolescents | Pain at the inferior aspect of the patella, subacute to chronic onset | Tenderness to palpation, occasionally swelling in region of tibial tubercle | None | Fracture, tendinitis of patellar tendon, tumor, osteomyelitis | Reassurance, analgesics |
| Chondromalacia | Young active persons, either gender | Subacute onset of patellar pain, worse walking stairs, little pain at rest | Reproduction of pain on pressing patella against femoral condyles | Synovial fluid noninflammatory, sunrise radiograph may reveal irregularity of articulating surface of patella | Tendinitis, bursitis, meniscal injury | Isometric quadriceps-strengthening exercises, NSAIDs, pure analgesics |
| Anserine bursitis | Middle age, elderly with OA, young active patients | Subacute onset of pain localized to the posteromedial aspect of knee | Point tenderness over anserine bursa, rarely palpable swelling | None | OA, medial meniscal injury | NSAIDs, local heat, local corticosteroid injection |
| Prepatellar bursitis | Those who kneel on hard surfaces, especially carpenters, plumbers, roofers, carpet layers | Subacute onset of pain in prepatellar area; swelling, erythema, desquamation, or purulent discharge suggests septic bursitis | Tenderness, erythema, fluctuant swelling of bursa anterior to patella, knee flexion may be limited but full extension possible without increased pain | Bursal aspirate, culture, Gram's stain, crystal search | Cellulitis, gouty bursitis, hemobursa, septic bursitis, patellar fracture, fat necrosis, erythema nodosum | If septic: antibiotics, repeated needle aspiration for drainage; if nonseptic: NSAIDs, local heat, activity modification |
| Osteoarthritis | Middle aged, elderly, athletes, obese, those with prior knee trauma | Progressive, pain, stiffness, decreased ROM over years, “cracking” of joint, no rest pain unless very advanced arthritis, short-lived morning stiffness (minutes) | Decreased ROM, swelling, crepitation, bony prominence | Synovial fluid noninflammatory, osteophyte formation, subchondral cysts, sclerosis, joint space narrowing seen on radiograph | Inflammatory arthritis, meniscal tear, anserine bursitis, secondary forms of OA: hemochromatosis, Wilson's disease, ochronosis, gout, acromegaly, hypothyroidism, hyperparathyroidism | Analgesics or NSAIDs, quadriceps-strengthening exercises, weight loss if appropriate, use of cane Consider surgical intervention (tibial osteotomy or total knee replacement) for unremitting pain |
| Malignancy | Metastatic cancer most common; primary bone and soft tissue sarcomas less likely; leukemia; lymphoma; myeloma | Slowly worsening pain, swelling, stiffness, prominent night pain is suggestive | Decreased ROM, diffuse tenderness, effusion | Synovial fluid with lymphocytic predominance, tumor cells sometimes seen, periosteal disruption or lytic bone lesions on plain radiograph; MRI defines bone and soft tissue involvement; biopsy if no known primary | Inflammatory arthritis, benign tumors, osteomyelitis | Primary tumors: surgical excision or amputation, adjuvant chemotherapy or radiation therapy |
| Metastatic tumors: radiation therapy for pain control, other treatment based on type of malignancy | ||||||
| MTP, Metatarsophalangeal joint;WBC, white blood cell count;RA, rheumatoid arthritis;NSAIDs, nonsteroidal antiinflammatory drugs;ROM, range of motion;RF, rheumatoid factor;ESR, erythrocyte sedimentation rate;IBD, inflammatory bowel disease;IV, intravenous;UTI, urinary tract infection;ECM, erythema chronicum migrans;PVNS, pigmented villonodular synovitis;OA, osteoarthritis;SLE, systemic lupus erythematosus;AVN, avascular necrosis;MRI, magnetic resonance imaging. | ||||||
[edit] Mechanical Disorders
Mechanical disorders of the knee may involve bone, cartilage, and periarticular structures such as bursae, tendons, and ligaments.
[edit] Fracture.
Most fractures within the knee involve the tibial plateaus or patella.A history of trauma followed by acute onset of pain and swelling suggests intraarticular fracture, and physical examination should be limited to assessing neurovascular integrity of the leg.Swelling and limited range of motion are usually present.The thigh, knee, and lower leg should be immobilized and radiographs obtained (AP, lateral, sunrise views).If a fracture is documented, aspiration may be deferred unless septic arthritis is strongly suspected as well.Occasionally the diagnosis of fracture is not definite even with radiographs.Aspirated synovial fluid may reveal a bloody effusion or frank blood, and Sudan red stain to detect fat droplets from the marrow should be performed.Computed tomography (CT) or MRI may help detect fractures not evident on plain films.The differential diagnosis includes other traumatic injuries (e.g., meniscal tear, ligamentous injury), other causes of hemarthrosis (e.g., pigmented villonodular synovitis), and bleeding disorders (e.g., hemophilia, anticoagulant therapy).Management of an intraarticular fracture includes immobilization and prompt orthopedic consultation.
[edit] Ligamentous Injury.
Ligamentous injuries often result from athletic injuries and frequently involve the knee.The history usually reveals pivoting on the knee after a jump, excessive extension, or medial or lateral stress.Often the patient describes the feeling of something “giving” within the joint, followed by acute onset of pain and swelling.[2] Joint laxity may be apparent if the ligament tear is complete.Physical examination may reveal swelling and, depending on the ligament involved, point tenderness over the medial joint line (medial collateral ligament) or lateral joint line (lateral collateral ligament).To test for a cruciate ligamentous tear, instability of the joint may be assessed with the anteroposterior drawer test. With the knee flexed 90 degrees, the examiner attempts to pull the tibia forward, away from the femur.If laxity is detected, an anterior cruciate ligament tear is likely.By reversing the force, the posterior cruciate ligament is tested.Medial and lateral collateral ligaments are tested by applying pressure on the lateral aspect of the knee, stressing the medial collateral ligament.These forces are reversed to test the lateral collateral ligament while the patient lies supine with the knee extended.Laxity indicates a collateral ligament injury.As with fractures, neurovascular examination is important.Although plain radiographs help rule out fracture, the imaging study of choice to diagnose ligamentous tears is MRI.Joint aspiration generally reveals either serosanguineous, noninflammatory fluid or a bloody effusion.Differential diagnosis includes meniscal tear, fracture, or sprain.Management for complete tear in active patients is usually surgical repair.
[edit] Meniscal Tear.
The two groups of patients likely to have meniscal tears are young adults with a history of trauma and middle-aged or elderly patients with osteoarthritis.Medial are more common than lateral meniscal tears.A meniscal tear presents with acute or subacute pain.Patients may experience the knee “giving way” or have painful popping or locking.On examination, swelling is common, with warmth and point tenderness over either the medial or the lateral joint line.Physical examination includes the McMurray's test, although a negative test does not exclude meniscal pathology.Diagnostic tests include radiographs to evaluate for fractures, osteoarthritis, and intraarticular loose bodies.Aspiration generally yields noninflammatory fluid that may be bloody, depending on the extent of the tear.The best imaging study to diagnose a meniscal tear is MRI, generally done only if the diagnosis is in doubt or surgical intervention is anticipated.Initial management is conservative: rest, crutches, and analgesics.If symptoms do not resolve within several weeks, orthopedic referral is appropriate.The differential diagnosis includes fracture, avascular necrosis, intraarticular loose bodies, and ligamentous injury.
[edit] Osteonecrosis.
Sickle cell anemia, corticosteroid therapy, decompression illness, alcoholism, trauma, SLE, and dyslipoproteinemias predipose to osteonecrosis, also known as avascular necrosis. Osteonecrosis presents as acute pain, sometimes accompanied by swelling.Physical examination may reveal an effusion and tenderness over the lateral or medial joint line.[3] Range of motion may vary.If the process has been limited and painful, an AP radiograph may reveal an area of sclerosis and collapse of the affected femoral condyle or tibial plateau.Patients who are examined earlier may have normal radiographs.At this stage, MRI is the diagnostic study of choice.A bone scan may also reveal changes before a plain radiograph does.The differential diagnosis includes fracture, meniscal tear, neoplasm, osteomyelitis, and osteoarthritis.Initial management is conservative, with rest, NSAIDs, and muscle strengthening.If this is not effective, orthopedic consultation is recommended for possible tibial osteotomy or, in the case of established secondary osteoarthritis, hemiarthroplasty or total knee replacement.[4][5][6]
[edit] Osgood-Schlatter Syndrome.
Osgood-Schlatter syndrome is a benign condition seen in adolescents.The patient complains of pain inferior to the patella.On physical examination, pain is elicited by palpation of the patellar tendon's attachment to the tibial tuberosity.The condition is typically self-limited and requires no therapy other than avoiding stress to the quadriceps tendon mechanism.
[edit] Chondromalacia.
Also known as the patellofemoral syndrome, chondromalacia is also a disease of predominantly young, active individuals, particularly women.This overuse syndrome often affects the weekend athlete.The onset of knee pain is often subacute and is worse with use, particularly on climbing stairs and standing up after sitting.At rest, pain is generally minimal.Physical examination may reveal an effusion and warmth.Pain may be reproduced by direct downward pressure of the patella against the femoral con dyles while the patient lies supine.Routine radiographs may reveal irregularity of the patella's undersurface.Synovial fluid is characteristically noninflammatory.The differential diagnosis includes tendinitis, bursitis, meniscal tear, andosteoarthritis.Management is conservative, with quadriceps-strengthening exercises and NSAIDs.
[edit] Anserine Bursitis.
Anserine bursitis generally affects middle-aged and elderly individuals with osteoarthritis of the knee, although it can occur in young, active individuals.Pain is subacute at onset and localized to the inferomedial aspect of the knee.Physical examination reveals point tenderness on palpation of the anserine bursa (see Fig.129-1).Signs of osteoarthritis of the knee may be found.The differential diagnosis includes osteoarthritis and medial meniscal injury.Management includes local corticosteroid injection, NSAIDs, heat, and ultrasound, which may be combined with topical 10% hydrocortisone cream.
[edit] Prepatellar Bursitis.
Also called housemaid's knee, prepatellar bursitis often results from prolonged kneeling on a hard surface and tends to be an occupational injury.Inflammation occurs in the prepatellar bursa (see Fig.129-1).Pain, swelling, and erythema over the patella are often present.Knee extension is generally full, but flexion is limited because of traction on the inflamed soft tissues.Relatively painless motion from full extension to about 90 degrees of flexion helps distinguish prepatellar bursitis from inflammation of the true knee joint.If a bursal effusion is present, aspiration of the bursa should be attempted.If fluid is obtained, WBC should be obtained.If the fluid is inflammatory, septic bursitis must be considered.Since fever, peripheral leukocytosis, and positive bursal fluid Gram's stain for bacteria may be present, aspirated fluid should be cultured.The differential diagnosis includes septic bursitis, patellar fracture, arthritis of the knee, and cellulitis.Management is conservative and includes NSAIDs, rest, protective knee pads, and avoidance of further trauma.If septic bursitis is likely, empiric antibiotics to cover staphylococcal and streptococcal species should be given after bursal fluid aspiration, Gram's stain, and culture.
[edit] Synovial Tumors
In general, tumors of the synovium and bone are rare causes of knee pain.The diverse malignancies that involve the knee include chondrosarcoma, synovial sarcoma, lymphoma, osteosarcoma, neuroblastoma, and metastatic carcinomas of many origins.Marrow involvement with leukemia may also produce knee pain, especially in children.Pain from knee involvement is similar, regardless of the underlying neoplasm, being subacute to chronic and becoming constant with progression.Swelling of the joint and decreased range of motion are variable.Physical examination may reveal knee warmth, swelling, restricted motion, effusion, and tenderness over the affected area.Routine radiographs may reveal disruption of the periosteum and trabeculae and a soft tissue mass.If plain films do not reveal changes, CT or MRI scans may suggest the disease.Biopsy is necessary for diagnosis and should be performed carefully to avoid seeding uninvolved tissues.Synovial fluid is usually inflammatory with a lymphocytic predominance.Tumor cells are sometimes seen in synovial fluid.Differential diagnosis includes inflammatory arthritis and infection with concomitant osteomyelitis, particularly if the leukocyte count is greater than 10,000.Local management includes radiation and surgical debridement.Fixation with intramedullary rods may be needed for large lytic lesions, which predispose to pathologic fracture.Systemic management is determined by the nature of the malignancy.
[edit] REFERENCES
- ↑ A Alvarellos, I Spilberg: Colchicine prophylaxis in pseudogout. J Rheu matol 1986; 13:804.
- ↑ J McCune,et al.: Evaluation of knee pain. Prim Care 1988; 15:795.
- ↑ H Mankin: Nontraumatic necrosis of bone (osteonecrosis). N Engl J Med 1992; 326:1473.
- ↑ Case report, N Engl J Med 316:736, 1987.
- ↑ P Lotke,et al.: Osteonecrosis of the knee. Orthop Clin North Am 1985; 16:593.
- ↑ H Spiera: Osteoarthritis as a misdiagnosis in elderly patients. Geriatrics 1987; 42:37.
