Effusion of the knee joint


The following anecdote will realize the importance of a coherent conduct face knee effusion.

M. Jacques C., 30 years, gardener, complains of pain and an increase in volume of the right knee. These symptoms occurred during his work after a shock and prolonged kneeling station. They are subject to an initial medical certificate of a work accident.

Fifteen days later, in the absence of improvement, the opinion of a surgeon is asked. A patellar shock on this protruding knee evidence to suggest an abundance of effusion. No abnormal movements may evoke a tendon-ligament injury. Radiographs of the knees show that the opacity of the effusion right. arthrography is then made. The medial meniscus does not seem perfect. On this argument, and at the continued effusion, meniscectomy is performed.

Nothing is arranged, on the contrary. The knee is swollen, become the nocturnal pain, the sedimentation rate is to 50 a mm 1 hour. For the first time the synovial fluid is examined. It is cloudy, contains 20 000 elements per ml which 90% polymorphonuclear. Although no germ grows in the culture of this liquid, fear of postoperative sepsis is undertaking a massive broad-spectrum antibiotics no other result than a few side effects.

The appearance on treatment of left knee pain will end this diagnostic error. Rheumatoid arthritis who started with a monoarthritis is finally recognized.

Where are the flaws or that led to these errors both in the choice of additional tests than for treatment?

* The first derailment comes from a misreading of history. The accident was admitted to inconsistent elements. An effort or stay long knees are not trauma and can generate an effusion. The coincidence between the appearance of pain and physical activity or sport is not enough to establish the relationship of cause and effect between these two events even if invoked by the patient often eager for simple explanations.

* The main referral error is the lack of examination of joint fluid. This gap is to misunderstand the nature of inflammatory arthropathy and sent for arthrography is of no use in arthritis.

* Moreover, biased in this clinical context, the interpretation of arthrography was tendentious. the revised post pictures showed no meniscal tear.Effusion of the knee joint

* The unknown arthritis continued to evolve after meniscectomy. But as the biological examinations (VS, study of synovial fluid) have been made only after the intervention, the diagnosis was again astray, this time to postoperative septic arthritis.

These diagnostics avatars even have forensic consequences especially for the patient. He will plead years, denying that “work injury” that had touched his knee enough to require surgery, itself complicated infection, is not the cause of rheumatic disease.

Driving the diagnosis leads in four stages.

effusion :

The first step must answer the question: effusion is it articular?

* The existence of a patellar shock or fluid wave allows to affirm and distinguish it from prérotulienne fluctuation characterizes a bursitis or bursitis of the crow's feet that seat to face supéro- internal tibia.

* Swelling fluctuating and not swinging the popliteal fossa evokes a popliteal cyst that is always satellite joint effusion.

Nature of the effusion :

The second step must determine the mechanical nature or inflammatory effusion.

Whatever the effusion seat, the answer to this question is obtained by history, the joint aspiration and synovial fluid.

* The appearance of the liquid may already guide:

– a translucent citrine yellow liquid is surely a mechanical liquid. Moreover, it is very viscous. A drop between the thumb and index finger protected by a glove form a thread 4 at 6 cm.

– a turbid liquid is an inflammatory liquid (the disorder is net as soon as the number of elements exceeds 5000 per ml).

* The cytological analysis of the liquid will provide the only two numbers needed for this ranking: the number of elements per ml and the percentage of polymorphonuclear.

– Less of 1 000 elements per ml and less than 50% polymorphonuclear, it is a mechanical liquid formula.

– More than 2 000 elements per ml or more 50% polymorphonuclear, it is a liquid of inflammatory formula.

– Between 1 000 and 2 000 cells / ml, the ranking will take into account the clinical context.

* The biochemical study, and in particular the determination of protein, does no more than bring the count of elements and is not necessary. A titre documentaire: protein greater than 40g / l inflammatory liquid, proteins suprérieures to 40g / l mechanical liquid.

The third step will take two directions depending on whether the liquid is of formula mechanical or inflammatory formula.

liquid inflammatory :

Arthritis is or may be microcrystalline :

clinical Orientation

microcrystalline arthritis is suspected of:

– a sudden onset.

– the existence of similar episodes in the past.

– the efficacy of anti-inflammatory drugs on these arthritides.

Some clinical features, family, radiological or biological allow to happen sooner or later the diagnosis of gout or chondrocalcinosis.

diagnostic certainty

The examination of the liquid between slide and cover claims without delay the diagnosis:

* The urate crystals are fine needles to tapered tip phagocytosed by polymorphonuclear:

– their length is close to the diameter of a polynuclear and they are clearly visible in the cytoplasm of these unstained cells examined between slide and coverslip.

– the crystals are sometimes tiny (2 microns). It is then, by following the movements of the cells, wait for the crystal embedded in the cytoplasm unmasks upon rotation.

– all urate crystals are highly birefringent in polarized light.

– the identification of crystals in their dissolution by uricase is not in common use, although often cited.

* calcium pyrophosphate crystals chondrocalcinosis (CCA) are intracellular or extracellular:

– they have 5 at 15 microns.

– their ends are square.

– they are not birefringent in polarized light.

* sick of the apatite crystals calcifications do not see knee. Tendon calcifications being, they are responsible for tenosynovitis and not of arthritis, except at the shoulder or the supraspinatus tendon can communicate with the joint through a gap in the rotator cuff.

* apatite debris more crystals described in the destructive arthropathy are not seen by the technical standards of examination of joint fluid.

* crystals Charcot-Leyden accompanying arthritis pseudo-allergic eosinophilic and cholesterol crystals associated with chronic inflammatory effusions are curiosities without phlogogenic property.

L’ Arthritis is or may be septic :

* Inflammatory liquid (so disorder) will be regarded as possibly septic until proven especially:

– it is a monoarthritis.

– arthritis is loud in its expression (daytime and nocturnal pain came "ing an impotence).

– it operates in an infectious context.

* The proof of the absence of infection will be provided:

– quickly by the discovery of microcrystals.

– or after 24 hours by the negativity of joint fluid cultures seeded on media that could allow the growth of various germs (banal germs, gonocoque).

– or after a longer period for other germs for which other diagnostic tools will be implemented as Brucella, Mycobacterium tuberculosis or fungal infection.

* Research germs by blood cultures and possible entry points is conducted in parallel.

* A biopsy of the synovial needle will, in doubt, histology and culture of synovial folds. The dosage of articular lactic acid, if it can be obtained emergency, can help eliminate septic arthritis banal germs if its rate is low.

The question is usually raised in 24 hours unless a blind prior antibiotic treatment levy has been started.

The liquid is inflammatory, sterile, without microcrystals :

It may nevertheless be of joint infections but by agents who do not grow on the usual media: Borrelia burgdorferi Lyme arthritis, of secondary syphilis treponema, virus (Parvovirus B19 5th disease, rubella, VIH).

Ignorance of these infectious arthritis does not currently have serious consequences on their development.

It's about, in most cases, aseptic inflammatory arthritis.

aseptic inflammatory arthritis :

* The fourth step will enable to classify this aseptic inflammatory arthritis in one of the major groups of inflammatory rheumatism:

– rheumatoid arthritis.

– spondylarthropathie.

– connectivity.

– vasculitis.

– Intermittent rheumatism and various rheumatism.

* This ranking is easier when the effusion of the knee joint is associated with signs or extra-articular in sufficient numbers to meet the criteria specific to each of these rheumatic diseases. If a pending diagnosis “monoarthritis of the knee” will be retained and a proposed symptomatic treatment.

fluid mechanics :

The mechanical liquid comprises less than 1 000 elements and less 50% polymorphonuclear.

In a young person under 40 years :

* Rather, it is an internal derangement of the knee but entered "already do some suffering from articular cartilage: meniscal lesion, joint instability by a crossed ligament injury, instability of the patella.

* It can also be a osteochondritis, a chondromatose synovial.

Arthrography and arthroscopy can be concluded these lesions and to treat some.

In a subject more 50 years :

* After 50 years, effusion mechanical knee formula is primarily a congestive osteoarthritis thrust, that is to say a progressive phase of the osteoarthritic disease or cartilage is being chondrolysis.

* The diagnosis of osteoarthritis will be done on radiographs of standing front knees, standing knees bent 30 ° (shot), profile and incidence patellofemoral 45 °.

– We can, on these pictures, measuring the height of interlining.

– These measures compared to those taken on prior or subsequent shots used to affirm the cartilage damage and have a numerical idea of ​​the speed of Chondrolysis.

osteonecrosis :

Effusion and knee pain suddenly settling on one knee hitherto clinically and radiologically normal must also mention after 50 years aseptic osteonecrosis.

It sits above the medial condyle lateral condyle and trochlea but are not spared.

Algodystrophie :

A dystrophy may also be accompanied by a mechanical nature of effusion.

The bone uptake on scintigraphic image can recognize sooner the etiology of these painful knees whose initial radiological examinations are normal.

special liquids :

liquid bleeding :

traumatic causes

Once removed sufficient traumatic injury to damage intraarticular structure likely to bleed (articular fracture, tearing osteochondral, severe sprain), must seek a medical cause.

medical causes

Medical causes of hemarthrosis to look for are:

* abnormalities of blood dyscrasias, haemophilia in children, anticoagulant therapy in adults.

* the advanced arthrosis of patellofemoral associated or not with chondrocalcinosis and recognized on the axial radiological impacts at 45 ° which is treated by rest and joint lavage.

* a benign tumor of the synovial, synovitis villonodular:

– identified on MRI with the very particular signal from the synovial loaded iron.

– affirmed and treated by arthroscopy showing villi in thick brown thermowells and hyperplasia and giant cell histology.

Liquids rich in eosinophils :

* An eosinophil count greater than 30% is seen only in a rare condition called “Pseudo-allergic arthritis” which also includes a dermographisme and high levels of serum IgE.

* Filarial arthritis can be rich in eosinophils. A small percentage of counts elements eosinophilic has no specificity that these cells are exceptionally observed in the synovial fluid.

liquids lymphocyte :

* It must first destroy a legend that a rich in-cell liquid is suggestive of joint tuberculosis. Fluid from a “white rising” of the knee is a common inflammatory liquid, rich in polynuclear.

* A liquid containing more than 70% lymphocytes might suggest sarcoidosis. It is also seen in some aggressive forms of rheumatoid arthritis, in arthritis syndrome Sjögren.

monocytic liquids :

Acute inflammatory arthritis which the liquid is made of 70% monocyte fact evoke arthritis Parvovirus B19 usually a joint location of a myelomonocytic leukemia.

some curiosities :

* The ragocytes or grapes to see cells are examined on a liquid fresh.

– They are lysosomal vacuoles enlarged green hue occupying the cytoplasm of granulocytes.

– Although particularly prevalent in rheumatoid arthritis of liquids •, the ragocytes can also be observed in other inflammatory origin liquids.

* Cells can contain inclusions:

– polymorphonuclear containing a homogeneous nuclear inclusion are a cell Hargraves which can be observed on the smear of a lupus arthritis synovial fluid.

– inclusions in the cytoplasm of macrophages are fairly common in spondyloarthritis without however being specific.

Conclusion :

Of the many lessons that can be drawn from the study of synovial fluid, we note the importance of those obtained by the simplest tests requiring only two blades, a coverslip, a vial Giemsa and microscope: counts elements, mark of microcrystals and the formulation of the liquid. We must add to send without delay any liquid bacteriology laboratory that is not citrine.

These simple tests allow the classification of arthropathy in: mechanical, septic inflammatory, aseptic inflammatory or inflammatory microcrystalline, necessary first step to any progress in the diagnosis and avoiding errors that may have adverse consequences.


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