Differential diagnosis of osteoarthritis

Ensuring effective therapy for osteoarthrosis and relapses of the disease largely depends on the use of standardized approaches to its diagnosis and differential diagnosis. Therefore, this article presents generally accepted differential diagnostic criteria and standards for assessing the arthrological status of patients with osteoarthrosis (including the SF-36, HAQ, AIMS, EuroQol-5DHflp questionnaires).

The application of these criteria and standards in practical medicine will allow doctors of various specialties (rheumatologists, therapists, orthopedic traumatologists, etc.) to take a unified approach to determining the stage, degree of severity of pathological signs, and assessing the functional state of the musculoskeletal system in osteoarthritis.

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Osteoarthritis diagnostic algorithm

1. Analysis of the anamnesis: taking into account the hereditary factor, injuries, inflammatory and metabolic lesions of the joints, vibration factors, sports activities, and the nature of work activities.
2. Assessment of orthopedic status: flat feet, posture, skeletal deformities.
3. Neuroendocrine status, regional circulatory disorders.
4. The nature of the course of the joint syndrome: slow gradual development.
5. Localization of lesions: joints of the lower extremities, hands, spine.
6. Clinical assessment of joint syndrome:
   1. pain of a “mechanical” type, increases with exertion and decreases at rest;
   2. the presence of periodic “blockades” of the joint;
   3. Joint deformation is caused primarily by bone changes.
7. Characteristic radiographic changes: subchondral osteosclerosis, narrowing of the joint space, intraosseous cysts, osteophytosis.
8. Absence of pathological changes in the hemogram, synovial fluid (in the absence of reactive synovitis).
9. Conducting differential diagnostics with the following arthropathies.

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Differential diagnosis of osteoarthritis

Most often, osteoarthritis is differentiated from arthritis of various origins - rheumatoid, infectious, metabolic.

1. Rheumatoid arthritis. Osteoarthritis of the knee joints and small joints of the hands (Heberden's and/or Bouchard's nodes) is often complicated by secondary synovitis, which in some cases can recur, requiring differential diagnosis with rheumatoid arthritis.

Osteoarthritis is characterized by a gradual, sometimes unnoticeable, onset of the disease, the onset of rheumatoid arthritis is often acute or subacute. Osteoarthritis is more often detected in women with a hypersthenic body type.

Morning stiffness in osteoarthritis is mild and does not exceed 30 minutes (usually 5-10 minutes).

Osteoarthritis is characterized by a "mechanical" nature of pain syndrome: pain occurs/increases during walking and in the evening hours and decreases at rest. Rheumatoid arthritis is characterized by an "inflammatory" nature of pain syndrome: pain occurs/increases at rest, in the second half of the night and in the morning hours, and decreases during walking.

Rheumatoid arthritis is characterized by predominant damage to small joints of the hands and feet, with arthritis of the metacarpophalangeal and proximal interphalangeal joints of the hands being pathognomonic. Osteoarthritis most often affects the distal interphalangeal joints (Heberden's nodes); damage to the metacarpophalangeal joints is not typical for osteoarthritis. It predominantly affects large joints that bear the greatest physical load - the knees and hips.

X-ray examination is of great importance in the differential diagnosis of osteoarthrosis and rheumatoid arthritis. X-ray images of joints affected by osteoarthrosis reveal signs of destruction of articular cartilage and increased reparative response: sclerosis of the subchondral bone, marginal osteophytes, subchondral cysts, narrowing of the joint space. Sometimes osteoarthrosis of small joints of the hands occurs with erosion of the articular edges, which complicates differential diagnosis.

Osteoarthritis does not cause the development of deformations characteristic of rheumatoid arthritis. Osteoarthritis rarely and slightly increases the level of acute-phase reactants ( ESR, CRP, etc.), and does not typically detect rheumatoid factor (RF) in the blood serum.

2. Infectious arthritis (septic, tuberculous, urogenital) can be differentiated due to their clear clinical picture (acute onset, rapid development and course, severe pain and pronounced exudative phenomena in the joints, hectic fever, shift in the blood formula, effect of etiotropic therapy).
3. Metabolic (microcrystalline) arthritis/arthropathies. Thus, gouty arthritis is characterized by acute, paroxysmal joint episodes, manifested by high local activity, localization of the process in the metatarsophalangeal joint of the first toe, clear radiographic changes.

Differential diagnostic signs of osteoarthritis and gouty arthritis

Sign	Osteoarthritis	Gout
Floor	Equally common in men and women	Mostly in men
Onset of the disease	Gradual	Acute, subacute
Course of the disease	Slowly progressive	Recurrent with acute attacks of arthritis
Localization	Interphalangeal joints of the hands, hip, knee joints	Mainly the joints of the first toe, ankle joints
Heberden's nodes	Often	None
Tofus	None	Often
Radiographic changes	Narrowing of the joint space, osteosclerosis, osteophytes	"Punchers"
Hyperuricemia	Absent	Characteristic
Kidney damage	Not typical	Often
ESR	It can be slightly increased	During an attack, it increases sharply.

Cases where clinical and radiographic signs of secondary osteoarthrosis are determined in a patient with chronic gout deserve special attention and differential diagnostics. Often these patients are mistakenly diagnosed with primary osteoarthrosis, and gout attacks, especially in their subacute course, are interpreted as recurrent reactive synovitis. It is necessary to take into account that pain in primary deforming arthrosis has a "mechanical" character, exacerbations of synovitis are milder, quickly disappear at rest, tophi and characteristic radiographic signs - "punches" are absent.

Differential diagnostics of coxarthrosis and coxitis in the early stages is especially difficult. The diagnostic signs given allow us to differentiate these diseases.

Problems often arise in the differential diagnosis of gonarthrosis with reactive synovitis and isolated arthritis of the knee joint (especially with the development of secondary osteoarthrosis). Taking into account the nature of the pain syndrome and radiographic signs, it is important to note the different severity of local inflammatory reactions, limitation of movement, as well as the specific nature of joint deformations.

Differential diagnostic signs of coxarthrosis and coxitis

Symptom	Coxarthrosis	Coxitis
Beginning and course	Slow, imperceptible	Sharper and faster
Nature of pain	Mechanical (under load, more in the evening)	Inflammatory (at rest, more in the morning)
Limitation of mobility	First of all, rotation and abduction of the leg	First of all, hip flexion
Blood changes indicating inflammation	None or minor	Expressed
X-ray	Minor osteosclerosis of the roof of the iliac fossa, punctate calcifications in the area of its upper edge, sharpening of the edges of the fossa of the head of the femur	Veiled radiographs in the periarticular tissue area (exudate), periarticular osteoporosis
ESR	Rarely up to 30 mm/h	Often high (30-60 mm/h)

Differential diagnostic signs of gonarthrosis and gonarthritis

Symptom	Gonarthrosis	Gonarthritis
Nature of pain	Mechanical or starting	Inflammatory
Local inflammatory reactions	Minor	Significant
Pain on palpation	Minor, only along the joint space	Significant, diffuse
Joint deformation	Mainly due to bone changes	Mainly due to changes in the soft periarticular tissues
Limitation of mobility	Weakly expressed	Sharply expressed, sometimes to the point of complete immobility
Inflammatory changes in the blood	None	Observed
X-ray of the joint	Osteosclerosis, osteophytosis, narrowing of the joint space	Osteoporosis, narrowing of the joint space, erosion of the articular surfaces, fibrous and bony ankylosis

Osteoarthritis of the knee joints and some other joints is sometimes difficult to distinguish from periarthritis, which has the same localization and course without pronounced inflammatory changes. In these cases, the clinical and radiological features of periarthritis are important:

• pain only with certain movements associated with areas of the affected tendon (for example, predominantly abduction of the arm with scapulohumeral periarthritis);
• restriction of only active movements, while passive ones remain in full range;
• limited pain on palpation (i.e. the presence of pain points);
• absence of signs of damage to this joint on radiographs;
• the presence of calcifications in soft periarticular tissues and periostitis.

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