The term „arthrosis“ is commonly used to describe the degenerative destruction of synovial joints. The full term “arthrosis deformans” is derived from the Greek word “arthron” and the Latin word “deformare” (deform).

In German speaking countries the acute form “arthritis” is separately used. Also chronic diseases with the focus on an inflammatory component are denominated with that term (e.g. rheumatoid arthritis).

In the Anglo-American literature the term „osteoarthritis” is also used for non-inflammatory forms. It seems that there is a trend to use separate terms as described above comparable to the German-speaking countries in recent publications.

The American College of Rheumatology defined osteoarthritis as a heterogeneous group of conditions that lead to joint symptoms and signs which are associated with defective integrity of articular cartilage, in addition to related changes in the underlying bone and at the joint margins. (Altman R, Asch E, Bloch D, Bole G, Borenstein D, Brandt K, Christy W, Cooke TD, Greenwald R, Hochberg M, et al. Development of criteria for the classification and reporting of osteoarthritis. Classification of osteoarthritis of the knee. Diagnostic and Therapeutic Criteria Committee of the American Rheumatism Association. Arthritis Rheum 1986;29-8:1039-49)

This definition has been adopted by the WHO (Reducing Risks, Promoting Healthy Life. World Health Report 2002. WHO, 2002).

The radiological changes related to osteoarthritis were classified by Kellgren and Lawrence into five levels of severity:

• 0 absence of radiological changes

• 1 questionable changes

• 2 minimal changes

• 3 moderate changes

• 4 severe changes

The original descriptions refer to the knee joint, the finger joints and the hip joint and were expanded to the spine and the shoulder etc. later on.

The typical radiological signs were described as:

• joint space narrowing and formation of subchondral sclerosis

• formation of osteophytes at the edge of the joint

• formation of periarticular ossicle

• formation of small pseudocystic areas with sclerotic margins typically in the subchondral bone

• and deformation of the bony joint partner

(Kellgren JH, Lawrence JS. Rheumatism in miners. II. X-ray study. Br J Ind Med 1952;9-3:197-207.

Kellgren JH, Lawrence JS, Aitken-Swan J. Rheumatic complaints in an urban population. Ann Rheum Dis 1953;12-1:5-15.

Kellgren JH, Lawrence JS. Rheumatoid arthritis in a population sample. Ann Rheum Dis 1956;15-1:1-11.

Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis 1957;16-4:494-502.

Kellgren JH, Lawrence JS. Radiological assessment of rheumatoid arthritis. Ann Rheum Dis 1957;16-4:485-93.)

Certainly there is a greyish zone from early forms of osteoarthritis to very obvious joint destruction that needs joint replacement which is not clearly defined. Terms like “early” or “mild” arthritis are not clearly defined either. Osteoarthritis is commonly believed to be a general joint disease that is certainly something different than local cartilage destruction, even if this is a great grade IV lesion according to Outerbridge. Additionally it is believed, that the process once started is a gradually downward spiral that cannot be returned with activation of certain processes at the molecular level, which are in the focus of basic research.

OA is the age related degenerated disease affecting the joint structure and function. There is damage to the cartilage and bone of the joints as a result of aggravated immune mediators like cytokines, interleukin's, etc. There is imbalance in the pro and anti inflammatory molecules. 

These mediators also aggravate the pain and other symptoms. Restriction of movement is the major debilitating factor. 

Thanks for the beautiful and concise review organised by J.K., the definition of "osteoarthritis (OA)" should has less controversy compared to its aetiology and pathogenesis. However, as part of the summary provided by J.K., the following statement is a common knowledge about OA: ".... it is believed, that the process once started is a gradually downward spiral that cannot be returned ...". This statement points out the common but somewhat misleading understanding that "osteoarthritis" is a "degenerative process like ageing". Therefore, the misnomer of "degenerative arthritis" has long been used interchangeable with "osteoarthritis" in the medical field and academia and paved the way to the current treatment guidelines for knee OA. Following the treatment guidelines laid by AAOS, OARSI and EULAR ..., it would not be surprised that some arthroscopic procedures will not be reimbursed by the insurance companies or health care systems as stated in this question. And I guess this is the main concern of this question. Dear P.N., Do you mind if I propose another more practical question from your question: "How could arthroscopists survive in the field of knee OA treatment under the global trend of unfriendly insurance policy for arthroscopic management of knee OA?"

Obviously, unless the targets of treatment for knee OA is clearly defined and the treatment effects are convincing, this global situation for arthroscopic managment for knee OA will not change. May be due to this global trend, in a recent international study, there are less than 20% orthopaedic surgeons "still" perform arthroscopy for knee OA patients. In my point of view, this might not be a good news for patients. Ten years ago, I faced the same situation in my country. However, after some years of struggling for publication of our research works (see the attached links), I could comfortably do arthroscopic management (ACRFP) for my patients and preserve their knees under our government insurance policy and it is no longer prohibited by them now. In my current practice, I mainly treat patients who suffer from knee OA. Each month, I usually see 100 referred patients with knee OA, for whom the initial course of action usually includes non-invasive measures under the guideline of KHPO. For some patients (around 30 of them), those are all the treatment they ever need to regain their freedom of movement and quality of life, but for the others (around 70 of them) whose pain persists, invasive therapies including ACRFP (around 50 of them) and arthroplasty (around 20 of them) become necessary. If you are interested in what I've done and experienced, it would be my pleasure to provide you more information.

http://journals.lww.com/md-journal/Abstract/2015/04040/Medial_Abrasion_Syndrome___A_Neglected_Cause_of.13.aspx#

http://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/1471-2474-13-226#

http://www.har-journal.com/wp-content/uploads/2015/08/HAR12-3059.pdf

This is a great discussion and also very informative. Allow me to add on this my humble views.

The definition of the word "Osteoarthritis" to start with creates some controversy on each own. It is a combination of mainly two words deriving from Greek (Ostoun=οστουν= Bone and Arthrosis = αρθρωσις = joint) and an ending (-itis=-ιτις)which is commonly used in Greek again for something infectious. In Osteoarthritis there is no infection. For this reason the ending -itis it is questioned and another ending -osis (-ωσης) was chosen as more appropriate. Despite this as -itis in some cases is liberally used for inflammation and in OA there is an inflamed joint then the original word can be used as well.

The role of Arthroscopy and OA.

Early '90 one of the pioneers in the study, the pathology, and the recreation of the articular cartilage, George Bentley, had said in one of his lectures at the instructional courses that "if we had available operating time to perform arthroscopic wash-outs of knees the course of the articular cartilage's changes in the knee joint may be different, and the need of total knee arthroplasty may be altered".

That was also the time when the number of "diagnostic arthroscopies" increased, not because of the above statement but also because of the use and the availability of the arthroscope to all "hands".

This increased the waiting lists of all hospitals and put pressure to managers who had to control them. The MRI started to be more available to all and the diagnosis with the use of the arthroscope it was thought that was not necessary and the risks of such procedure were higher that the MRI. This was taken by the insurances and they slowly stopped funding the "diagnostic arthroscopies".

The new though way which is used and it is possible to lead to acceptance from the insurances is "Staging of the Knee Degeneration" to define the exact prosthesis which could be chosen or define another way of treatment for the diseased articular cartilage.

Clinical definition of OA must be based on the clinical signs of OA. Pain (frequency, severity, effect on life), Stiffness, Deformity, Limitations of day living, Functional problems, Joint appearance etc. Oxford scoring, for example, can give answers to this. 

Small addition to the above:

Staging of the Knee Degeneration would be considered necessary because the patient's clinical picture is not corresponding with the patient's radiological findings.

I agree with G.Z.'s comment about the importance of clinical staging of knee OA. Most patients come for their symptoms (pain, tightness, discomfort, cannot walk for a distance, difficult in climbing .....) which might mainly related to either acute or chronic inflammation rather than deformity. Although patients seldom ask for correction of their deformity rather than releasing symptoms, we orthopaedic surgeons are taught to focus on the conventional x-ray staging to gauge the severity of the disease and make the decision for the necessity or methods to correct the deformity. This classical thinking process might loss the golden stage of treating or even curing this disease.

In a recent study (the first attached link), we found that medial plica-related MAS (medial abrasion syndrome) in middle and old age is a common but little recognised clinical condition. We defined this syndrome by investigating its clinical presentations, including predisposing factors, symptoms, signs, radiographic manifestations, and arthroscopic findings, and determined that it was a common cause of knee pain in this age group; we recommend that MAS be taken into consideration during the differential diagnosis and postulate that MAS can be effectively treated using AMR (arthroscopic medial release). In addition, our findings of the coincidence of knee OA and MAS (95% of coincidence) and the encouraging outcomes by treating them using AMR might assist in identifying a target for treatment of this common disease. Our practice according to this finding has devised an arthroscopic treatment option called arthroscopic cartilage regeneration facilitating procedure (ACRFP, see the second link) in 2004 that has (1) relieved thousands of patients of their knee pain without using analgesics, (2) helped open up the joint space in their knees, (3) improved their mobility, and (4) saved their knees from arthroplasty. The findings of our studies might provide some important information for arthroscopist interested in the treatment of knee OA.

When doing research reviews about knee OA, one question always emerged: why the classical classification of Kellgren and Lawrence still widely used in mordern medicine? During that 1950+, the imaging information could only be obtained by plain films, not to mention the lack of direct visural evidence such as arthroscopy. There were not rare occasions that we found grade III-IV focal cartilage lesions in the radiographic K-L stage II knees by arthroscopy in patients with obvious clinical symptoms. Although the sophisticated classifications recommended by OARSI and others focused on the morphologic changes of cartilage could provide precise and reproducible standards for outcome studies, we might need more simple and staightforward classification (such as Table 1 and 2 of the 3rd attatched link) for daily practice in the decision making of the treatment options.  

http://journals.lww.com/md-journal/Fulltext/2015/04040/Medial_Abrasion_Syndrome___A_Neglected_Cause_of.13.aspx

http://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/1471-2474-13-226#

http://www.har-journal.com/wp-content/uploads/2015/08/HAR12-3059.pdf