1 Arthritis of the Knee: Diagnosis and Management F
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3 1 1 1 Arthritis of the Knee: Diagnosis and Management F. P. Luyten, R. Westhovens, V. Taelman Summary Major advances in our understanding of the molecular basis of arthritic diseases has led to the development of In this chapter,an algorithm for the diagnosis of a painful new targeted therapies with a profound impact on the and swollen knee is presented. Arthritis of the knee can management of patients with rheumatoid arthritis and be restricted to a monoarticular clinical manifestation,or the spondyloarthropathies. it may be part of an oligo- or polyarticular disease.A care- ful anamnesis and clinical examination will allow the clinician to classify the clinical presentation of arthritis of Algorithm for Diagnosis of the the knee into disease groups such as osteoarthritis, Arthritic Knee rheumatoid arthritis, spondyloarthropathy, or miscella- neous arthritic diseases.These disease entities are briefly When one is confronted with a patient who has a painful, discussed and their therapeutic approaches reviewed. swollen knee, a well-structured approach is helpful for Finally,the case is made for a more routine use of synovial forming a working hypothesis and ultimately critical for biopsies in daily clinical practice, for diagnosis and to arriving at the most likely diagnosis. evaluate targeted therapies. The most important tool we have in a diagnostic workup is the clinical history, which must be as complete as possible.A patient can say what brings him to your of- Introduction fice,but in most cases precise and well-directed questions are needed to obtain critical information. Taking a Appropriate treatment of arthritis of the knee starts with complete history is a demanding task,but a lot of circum- correct diagnosis of the underlying disease and identifi- stantial evidence can evolve from a full history of the cation of the causes of the condition.Therefore,in the first current problem, past medical conditions, and the family part of this chapter we propose a comprehensive and history. practical algorithm for dealing with “arthritis of the The nature of the pain belongs to “the basics”, knee”, typically with signs and symptoms of pain, whether it be mechanical, inflammatory, neuropathic, or swelling, and loss of motion and function, separately or poorly defined. Mechanical pain occurs when the joint is in combination. Subsequently, we discuss clinically im- used: walking becomes difficult, and especially climbing portant separate disease entities such as osteoarthritis, stairs causes problems.On resting,there is less pain.Start- knee involvement in the major groups of chronic inflam- ing pain and stiffness are very characteristic of a more ad- matory arthritis – rheumatoid arthritis and the spondy- vanced mechanical pain pattern. loarthropathies –, and some miscellaneous forms of Inflammatory pain typically presents at night. More arthritis of the knee, perhaps less frequent but certainly specifically, the second part of the night is troublesome, clinically relevant, such as crystal-induced arthritis, sep- and patients need to get out of bed and move. They ex- tic arthritis, and Lyme disease. In these discussions we perience morning stiffness for at least 1 h, and this stiff- highlight the predominant clinical features and recent ad- ness diminishes progressively as the patient begins to vances in therapeutic options.Special attention is given to move. the concept of spondyloarthropathies, since this has still When pain is neuropathic in origin,a typical distrib- apparently not entered the daily practice of many physi- ution pattern corresponding to the innervation is found. cians. Finally, we discuss in more detail the synovium of Psychosomatic pain has no typical presentation or the knee, as this is easily accessible and has received in- distribution.Complaints are always more impressive than creased attention from rheumatologists.Indeed,through the clinical findings. the study of synovial biopsies we have gained increasing Additional questions can help the clinician to identi- insight into the pathophysiology of chronic arthritis. fy the problem as acute/subacute or a chronic arthritis. 4 I . Essentials 1 Painful and swollen knee ᮣ Yes ?Noᮣ Trauma Mechanical? Description of traumatic event ᮣ ᮣ ᮣ Yes No ᮣ ᮣ Clinical examination Monoarthritis? Additional Anamnesis ᮣ ᮣ ᮣ + Clin. Examination Joint aspiration No Yes ᮣ ᮣ ᮣ ᮣ X-rays Suspected Diagnosis Oligo/Polyarticular Joint aspiration Joint aspiration ᮣ ᮣ ᮣ ᮣ Arthroscopy MRI ᮣ ᮣ Infectious Crystal-induced Inflammatory X-rays ᮣ ⊡ Fig. 1-1. Algorithm flow chart for ᮣ Referral to specialist the patient presenting with a painful ...RA, SpA and swollen knee How long has the knee problem existed? When pain and When the knee is swollen and the presence of intra- swelling have been present for less than 6 weeks,the prob- articular joint fluid is suspected, arthrocentesis should lem is acute. Beyond 6 weeks' duration, the term chronic be performed. The results of the white blood cell count is used and implies that spontaneous healing of the and cell differentiation,Gram staining,bacterial culture, arthritis is unlikely. How acutely did the problem occur? and detection of crystals of urate or pyrophosphate are Suddenly, as seen in trauma, within hours, which is more diagnostic in case of infectious arthritis, gout, or pseu- likely in septic and crystal-induced arthritis,or over days do-gout. The white blood cell count in the synovial flu- or weeks, as in rheumatoid arthritis? id differentiates between a non-inflammatory problem Ask the patient whether this is the first time he has ex- (<2000 WBC/mm3), an inflammatory picture (2000–20 perienced arthritis of the knee or if he has had knee or 000 WBC/mm3), a strongly inflammatory picture such other joint problems in the past. This may provide hints as in crystal arthritis (20 000–50 000),and a most prob- as to whether it is a problem in a single joint or an oligo/ able septic arthritis (WBC >50 000 with >75% PMN). polyarticular disease. Finally, it is important to establish whether the knee It is also important to look for circumstantial evi- problem is a genuine monoarthritis or rather one where dence.Did trauma occur just before the knee swelling be- multiple joints are involved. The latter is classified as gan? Did the patient have an episode of fever? Did the oligoarthritis when fewer than five joints are involved, or patient experience an infection such as angina, gastro- as polyarthritis when five or more joints are inflamed. In enteritis, or urethritis? Does the patient have other clini- addition, assessments of symmetrical or asymmetrical cal conditions that could be linked to the knee arthritis, joint involvement are performed. such as skin problems (psoriasis, erythema nodosum), A few typical clinical entities, most frequent in daily chronic diarrhoa as seen in inflammatory bowel disease, clinical practice, are briefly presented. eye problems such as uveitis or scleritis? In this setting a complete familial history can also add useful informa- tion. Monoarthritis, Mechanical in Origin Thereafter, a clinical workup including a complete joint assessment and a full clinical examination, evaluat- Once the knee pain is recognized as mechanical,the most ing all the peripheral joints and the axial skeleton, can likely diagnosis in the older patient is osteoarthritis with provide further clues to the diagnosis and help to local- or without a meniscal or ligamentous pathology. Further ize the problem to the joint, periarticular structures, or investigations can be limited to standard weight-bearing muscle. It is not always trivial to distinguish a synovitis X-rays. from joint pain by intra-articular swelling, the distinction In younger people, mechanical pain will more likely being crucial for the diagnosis. For instance, a diagnosis be associated with a meniscal or chondral/osteochondral of rheumatoid arthritis requires a (poly)synovitis; in- problem or defect. Further investigations include MRI, flammatory polyarthralgia is not sufficient. CT-arthrography, and arthroscopy. 5 1 Chapter 1 · Arthritis of the Knee: Diagnosis and Management – F.P. Luyten et al. Acute Inflammatory Monoarthritis sentation (both knees, hands) in middle-aged and older of the Knee individuals. The signs and symptoms are usually local and restricted to one or both knees, sometimes associat- With inflammatory knee pain and swelling the differen- ed with hand OA or more generalized OA. Pain is by far tial diagnosis is far more complex.Acute monoarthritis of the predominant symptom, relieved by rest and without the knee is infectious until proven otherwise. Previous night pain or morning stiffness, but, especially in more arthrocentesis, skin wounds, typically on lower leg re- advanced disease, there is pronounced pain at the begin- gions or the feet, should be asked about and looked for. ning of movement. It is still unclear what causes the pain Fever is not always present, certainly not in the immuno- in OA. Most probably it is caused not by the cartilage, as compromised patient. Arthrocentesis is mandatory for this tissue has no nerve supply, but rather by the sub- bacterial examination and culture.Gram staining and the chondral bone and other intra- and periarticular struc- white blood cell count can be quickly obtained and are tures such as synovium, menisci, and ligaments. Acute mostly sufficient to begin antibiotic treatment. Arthro-