Osteoarthritis: clinical diagnosis and criteria

Osteoarthritis is a disease of the entire joint, affecting the hyaline cartilage, subchondral bone, synovial membrane, ligaments, and periarticular muscles. Clinical diagnosis is based on a typical pain profile, brief morning stiffness, and characteristic physical signs, and imaging is not necessary in standard situations. This approach expedites diagnosis, reduces unnecessary testing, and allows for immediate treatment. [1]

The key idea of the modern approach is that, in adults over 45 years of age with a typical presentation, diagnosis is established based on complaints and examination, without mandatory imaging. Imaging methods are prescribed for atypical presentations, alarming symptoms, or when planning surgery. This is reflected in recommendations that emphasize "clinical diagnosis" and the judicious use of imaging techniques. [2]

Osteoarthritis is highly prevalent and a leading cause of disability, making accurate clinical diagnosis a priority for primary care. Early identification of symptoms helps adjust loads, initiate exercise, and behavioral interventions, which slows progression and delays surgical decisions. [3]

Understanding pain mechanisms is important for the correct interpretation of complaints. Pain severity is influenced not only by the degree of structural changes on imaging, but also by low-grade synovitis and central sensitization, which is why pain intensity may not correspond to the radiographic appearance. This explains the variability of symptoms and the need to focus primarily on clinical manifestations. [4]

Table 1. "Clinical triad" for diagnosis without visualization according to current recommendations

Component	Content
Age	45 years and older
Pain	Increases with activity and decreases at rest
Stiffness	Absent or lasts no more than 30 minutes in the morning

Source: Clinical practice guidelines for diagnostics without routine imaging. [5]

How to recognize osteoarthritis during a doctor's appointment: complaints and examination

Typical complaints include deep mechanical pain in the affected joint, which intensifies with walking, climbing stairs, carrying heavy objects, or standing for long periods, and subsides with rest. A "crunching" sound during movement, a feeling of "tiredness" in the joint by the end of the day, and short-term morning stiffness are often noted. [6]

During examination, note localized tenderness along the joint space, crepitus with active movements, bony thickening along the joint margin, moderate swelling without obvious signs of inflammation, and limited range of motion. Effusion may be present in the knee joint, nodes at the distal and proximal interphalangeal joints in the hands, and limited internal rotation in the hip joint. [7]

Knee pain is characterized by increased pain when descending stairs and difficulty rising from a chair. Hip pain is characterized by groin or gluteal pain with limited internal rotation and flexion. Hand pain is characterized by pain at the base of the thumb and bony thickening of the distal interphalangeal joints. These clinical "patterns" increase the reliability of the diagnosis at the initial examination. [8]

A discrepancy between moderate radiographic changes and severe pain occurs in some patients due to the influence of synovitis and central sensitization. Therefore, treatment decisions are based on symptoms and functional limitations, not solely on imaging data. [9]

Table 2. The most common clinical signs during examination

Sign	What is observed most often?
Local pain	Along the line of the joint space during palpation
Crepitus	During active movements
Limitation of movement	At the end of the range of motion, especially rotation in the hip joint
Bone thickenings	Periarticular growths and osteophytes
Moderate effusion	Most often in the knee joint, without pronounced hyperemia

Source: Clinical reviews and guidelines for the management of osteoarthritis. [10]

Step-by-step algorithm for clinical diagnostics

Step 1: A detailed survey: The location of the pain, its relationship with activity, the duration of morning stiffness, factors that increase or decrease symptoms, and the impact on daily activities and sleep are clarified. Injuries, surgeries, obesity, concomitant diseases, and medication effects are identified. [11]

Step 2 - Targeted examination: gait, limb axis, tenderness on palpation, crepitus, range of motion, and signs of effusion are assessed. For the hip joint, internal rotation is important to examine, and for the knee joint, pain tests on load and functional tests of standing are important. [12]

Step 3 - Check for "red flags": a "hot" red joint, fever, sudden onset of severe pain and swelling, recent significant trauma, rapidly progressing deformity, neurological impairment. If any of these signs are present, urgent evaluation and exclusion of alternative pathologies is required. [13]

Step 4 - decision on additional studies: in the case of a typical picture in adults over 45 years of age, the diagnosis is established clinically without visualization, and studies are prescribed in the case of an atypical course, alarming signs, ineffectiveness of initial measures or preoperative planning. [14]

Table 3. Red flags for joint pain and initial actions

Situation	What to exclude first	Primary actions
"Hot" red joint with fever	Suppurative arthritis	Urgent puncture and microbiological examination of synovial fluid
Sudden severe pain and swelling without injury	Crystal arthritis	Synovial fluid analysis with crystalloscopy
Rapidly increasing deformation or instability	Fracture, ligament rupture, osteonecrosis	Urgent visualization and consultation with a specialist
Recent significant injury	Fractures, intra-articular injuries	Targeted visualization according to indications
Neurological deficit or pelvic dysfunction	Root compression, cauda equina syndrome	Emergency hospitalization and neurosurgical evaluation

Source: Standards for the acute evaluation of joint pain and clinical guidelines. [15]

The Role of Visualization: When is it Really Needed?

Routine imaging does not improve outcomes in patients with typical clinical presentations and should not be routinely ordered. Images are required in cases of atypical presentations, suspected alternative pathology, rapid deterioration, the need for preoperative planning, or diagnostic doubt. [16]

If imaging is indicated, the first method of choice is radiography, preferably with knee joint loading, which allows for assessment of the degree of joint space narrowing and osteophytes. Magnetic resonance imaging, ultrasound, and computed tomography are used selectively based on clinical indications. [17]

European guidelines emphasize the judicious use of imaging in the clinical management of peripheral osteoarthritis: the choice of method should be appropriate to the clinical question, and the results should be interpreted in conjunction with symptoms and physical findings. This prevents overdiagnosis and overprescribing. [18]

Radiographic assessment of severity is often performed using the Kellgren-Lawrence scale, which is based on osteophytes and joint space narrowing. It should be noted that the grade on this scale does not always correlate with pain intensity, so the clinical picture remains decisive. [19]

Table 4. When to order imaging for suspected osteoarthritis

Clinical situation	Selection method	Why is it prescribed?
Typical clinical picture in an adult over 45 years of age	Do not prescribe routinely	Clinical diagnosis
Atypical course or doubts	X-ray	Confirmation of bone changes, preoperative planning
Severe effusion, suspected synovitis or extra-articular structures	Ultrasound examination	Fluid and soft tissue imaging
Suspected intra-articular injuries, osteonecrosis, atypical pain	Magnetic resonance imaging	Detailing of cartilage, bone, menisci and ligaments
Complex anatomical cases	Computed tomography	Subtle bone anatomy and intervention planning

Source: National and European guidelines for the use of visualisation. [20]

Laboratory tests and joint puncture

There are no specific laboratory markers for osteoarthritis, so tests are used to exclude alternative diagnoses or in cases of atypia. In cases of typical presentation, laboratory tests are not required. If necessary, a complete blood count and inflammatory markers are ordered, based on the clinical context. [21]

Joint puncture is indicated for severe effusion of unknown origin, suspected purulent processes, or crystalline arthritis. Synovial fluid analysis includes cytosis, crystallography, and culture, allowing for rapid differentiation between emergency conditions and exacerbations of degenerative disease. [22]

Normal or moderately altered inflammatory parameters do not exclude or confirm osteoarthritis. Laboratory data are always interpreted in conjunction with clinical and physical examination data to avoid overdiagnosis of inflammatory arthritis. [23]

Prescribing broad antibody panels without an indication is not recommended, as it increases the risk of false-positive results and unnecessary patient anxiety. The choice of tests is determined by the likelihood of an alternative diagnosis based on the results of the interview and examination. [24]

Table 5. Laboratory tests for suspected alternative pathology

Situation	Target test	Purpose of appointment
Suspected purulent arthritis	Synovial fluid culture	Confirmation of infection and choice of therapy
Acute monoarthritic attack	Crystallography of synovial fluid	Detection of uric acid or calcium pyrophosphate crystals
Suspected inflammatory arthritis	Inflammatory markers and serological tests as indicated	Confirmation of systemic inflammation
Systemic symptoms of unknown origin	Basic blood tests	Exclusion of concomitant causes of pain syndrome

Source: clinical guidelines for the diagnosis of joint diseases. [25]

Differential diagnosis: how not to miss another disease

Inflammatory arthritis often presents with prolonged morning stiffness lasting more than 60 minutes, nighttime pain, swelling with warmth, and symmetrical involvement of the small joints of the hands. The presence of systemic manifestations and laboratory signs of inflammation increases the likelihood of an inflammatory nature. [26]

Crystal-induced arthritis typically presents with sudden, severe pain and swelling in one joint. Gout typically affects the first metatarsophalangeal joint, while calcium pyrophosphate arthropathy typically affects the knee and wrist. Diagnosis is made by detecting crystals in the synovial fluid. [27]

A purulent process must be ruled out in cases of a "hot," red joint and fever, as delay leads to joint destruction and septic complications. In such situations, puncture and initiation of targeted therapy are the priority. [28]

Pain originating from tendons, bursae, and periarticular structures often mimics intra-articular pain, but is aggravated by specific stress tests and is not accompanied by significant morning stiffness. A thorough examination helps distinguish extra-articular sources of pain. [29]

Table 6. Differences between osteoarthritis and other causes of joint pain

Sign	Osteoarthritis	Inflammatory arthritis	Gout	Calcium pyrophosphate arthropathy	Suppurative arthritis
Morning stiffness	Usually no more than 30 minutes	Often more than 60 minutes	Unstable	Unstable	Often expressed
Start	Gradual	Gradual	Sudden	Sudden	Sudden
Local signs of inflammation	Mild or moderate	Frequently expressed	Bright in attack	Bright in attack	Almost always expressed
Typical localization	Load-bearing joints	The small joints of the hands are symmetrical	First metatarsophalangeal joint	Knee, wrist	Any joint
Key test	Clinical picture	Inflammatory markers and serological tests	Crystalloscopy	Crystalloscopy	Synovial fluid culture

Source: national and international guidelines for differential diagnosis. [30]

Radiographic scales: how to use them and what not to expect

The Kellgren-Lawrence scale is useful for standardizing descriptions and scientific reporting, relying on osteophytes and joint space narrowing. However, pain severity and functional limitations depend on more than just radiographic features, so clinical decisions should not be based solely on this scale. [31]

Even with minimal changes on imaging, some patients may experience severe pain due to synovitis and central sensitization. Conversely, with significant osteophytes, symptoms may be moderate. This desynchronization emphasizes the priority of clinical assessment. [32]

Radiographic features are not always helpful in identifying early osteoarthritis. Studies on early criteria suggest combining clinical assessment, high-resolution imaging, and risk assessment, but these approaches have not yet been standardized for routine practice. [33]

In daily practice, scales are used to describe the severity of structural changes and to communicate with surgeons when planning interventions, but the initial treatment decision is determined by the patient's symptoms, goals, and functional limitations. [34]

Table 7. Kellgren and Lawrence scale: main levels

Level	Key radiographic features
0	There are no signs of osteoarthritis
1	Questionable narrowing of the space and possible marginal osteophytes
2	Certain osteophytes and possible narrowing of the space
3	Multiple osteophytes, distinct narrowing of the gap, possible deformation
4	Large osteophytes, pronounced narrowing of the gap and bone deformation

Source: original description and modern reviews of the scale. [35]

Scales and questionnaires for recording symptoms and function

The Western Ontario-McMaster University Osteoarthritis Index, the Knee Outcome Scale, and the Hip Outcome Scale are used to monitor symptoms and function. They help to objectively measure pain, stiffness, and functional limitations and compare the patient to themselves over time. [36]

Questionnaires are useful at the start of treatment and over time, for example, after 8-12 weeks, to assess the effectiveness of non-drug measures and the need for escalation of therapy. They do not replace clinical diagnosis but rather complement it with a quantitative assessment of symptoms. [37]

Simple functional tests such as the 30-second chair stand test and the six-minute walk test are of practical value, reflecting the actual performance of the joint and helping to discuss goals and progress with the patient. [38]

The choice of instrument should be discussed with the patient, taking into account the affected joint, lifestyle, and priority activities. Regularly recording results increases treatment adherence and makes the effects of exercise and weight management visible. [39]

Table 8. Instruments for assessing symptoms and function

Tool	What does it measure?	When to apply
Western Ontario and McMaster University Osteoarthritis Index	Pain, stiffness, function	At the start and every 8-12 weeks
Knee Outcome Scale	Pain, symptoms, daily activities	For knee osteoarthritis
Hip Outcome Scale	Pain, symptoms, daily activities	For hip osteoarthritis
Visual analog pain scale	Intensity of pain	At every visit
Quality of Life Questionnaire	Impact on everyday life	Every 3-6 months

Source: Reviews and clinical practice on outcome assessment in osteoarthritis. [40]

Special situations: early osteoarthritis and young age

In individuals under 45 years of age with post-traumatic injuries, obesity, or heavy loads, early symptom development with minimal radiographic changes is possible. In such cases, the emphasis is on a thorough clinical assessment, risk factor modification, and targeted exercise. [41]

Studies have proposed criteria for early knee osteoarthritis that combine clinical presentation and advanced imaging when indicated, but these approaches remain the subject of scientific debate and do not replace the standard clinical algorithm in primary care. [42]

In cases of obesity and muscle weakness around the joint, symptoms can be disproportionately pronounced. Weight management and an exercise program often reduce pain and improve function even without visible changes on imaging. This confirms the priority of a clinical approach. [43]

In cases of doubt and atypia, a low threshold for consultation with a rheumatologist or orthopedist is recommended to promptly exclude alternative diagnoses and discuss management options, including surgical ones.[44]

When to refer to a specialist and for surgical consultation

Indications for referral to a rheumatologist include prolonged morning stiffness for more than 60 minutes, significant signs of inflammation, systemic symptoms, rapid deterioration, and multiple symmetrical involvement of small joints. The goal is to exclude inflammatory arthritis and other systemic diseases. [45]

Indications for orthopedic consultation include significant functional limitations, persistent pain unresponsive to optimized non-pharmacological and pharmacological therapy, and significant structural changes with loss of support function. The decision is made in consultation with the patient based on individual goals and expected benefits. [46]

Before referral, it is important to assess symptoms using questionnaires, document the ineffectiveness of conservative measures, and, if necessary, perform radiography for planning. This facilitates communication between levels of care and expedites decision-making. [47]

In urgent cases described in the “red flags” section, referral should be urgent with initial diagnostic measures performed on site, including puncture if a purulent process is suspected. [48]

Brief conclusions for practice

1. In the typical presentation in adults over 45 years of age, the diagnosis of osteoarthritis is made clinically by activity-related pain and short-term morning stiffness, without routine imaging.[49]
2. Imaging is prescribed sensibly: radiography is indicated, and other methods are strictly targeted based on the clinical question. Results are interpreted only in conjunction with symptoms. [50]
3. Differential diagnosis is mandatory in cases of atypia or “red flags”, where the priority is the rapid exclusion of purulent and crystalline processes. [51]