There are no specific laboratory tests for this disease, but it can be further differentiated from other diseases. Blood sedimentation is normal in most patients, C-reactive protein is not increased, and rheumatoid factor is negative. The joint fluid is yellow or straw yellow with normal viscosity and a normal coagulation test, and its leukocyte level is less than 2 × 109/L. The sugar level is rarely less than 50% of the blood glucose level.
X-rays of the joints are helpful in the diagnosis of this disease. The following changes are seen in the affected joints on X-ray depending on the severity of the disease: narrowing of the joint space; sclerosis of the subchondral bone; bone artifact formation at the joint edge; cystic changes in the subchondral bone and, in rare cases, ship chisel-like bone changes; bone deformation including flattening of the femoral head and/or subluxation of the joint. It should be noted that many of those with the aforementioned radiographically affected changes do not have clinical symptoms of the disease.
Common reference points for the diagnosis of osteoarthritis
A detailed medical history plays an important role in the diagnosis of osteoarthritis, including age, number, location and degree of affected joints, nature of pain, presence or absence of morning stiffness and relationship to activity, etc.
Physical examination: including local pressure pain of the affected joint, swelling of the joint, rubbing sensation of the large joint, deformity of the joint, limitation of movement and even subluxation of the joint. Squatting pain indicates patellofemoral joint involvement, and when the hand holds the patella and extends and flexes the knee joint, an abrasive sound can be felt under the patella.
Imaging: Imaging tests that can help diagnose and treat osteoarthritis include ultrasound, X-ray, magnetic resonance imaging, arthroscopy, etc. Among them, arthroscopy is the gold standard for the diagnosis of osteoarthritis, which can directly observe the swelling and wear of joint cartilage, clarify the site of meniscal rupture and the degree of degeneration, as well as the degree of synovial hyperplasia. However, arthroscopy cannot show the deep cartilage changes and subchondral bone changes, and the joint examination is invasive. x-ray plain film cannot reflect the early cartilage lesions, and as the disease progresses, in the middle and late stage x-ray may show joint space narrowing, subchondral bone cystic changes, joint edge bone superfluity formation, etc., and in the late stage, joint free body or even joint subluxation may appear. MRI can show early articular cartilage degeneration, subchondral bone sclerosis, small cystic changes, knee joint cruciate ligament relaxation and thinning, meniscal degeneration, tears and bursal lesions, joint cavity effusion and other lesions, which has a greater role in guiding the diagnosis and treatment, but expensive is its disadvantage.
Fourth, serological testing: the more widely used clinical C-reactive protein is a good indicator of monitoring disease activity. With the continuous research on the pathogenesis of OA, in recent years, some promising markers of disease activity have been discovered.
Diagnosis and differential diagnosis The American College of Rheumatology (ACR) has developed the following classification criteria for osteoarthritis;
(a) Hand joint criteria Those who have hand joint pain or stiffness with at least three of the following four
1.The distal and proximal phalanges of the 2nd and 3rd fingers of both hands and the first carpometacarpal joint, 2 or more of these 103 joints show hypertrophy of the hard tissue.
2. At least 2 distal phalanges have hypertrophy.
3. Less than 3 metacarpophalangeal joints are involved (swollen).
4.At least 1 of the above 10 joints is deformed.
(B) Knee joint criteria Knee pain and X-rays of the knee show bone arthrosis, which is accompanied by any of the following.
1. Age >50 years.
2. Stiffness of the affected knee <30 min.
3. There is bone friction sound.
(C) Hip joint criteria Hip pain with at least two of the following three conditions
1.Blood sedimentation <20mm/1sth
2.X-ray shows bone artifact in the femur or femoral head
3.X-ray shows at least joint cavity narrowing
Osteoarthritis should be differentiated from the following diseases.
Rheumatoid arthritis Both accumulate finger joints, knee joints, etc. However, rheumatoid rheumatism is prominent with lesions in the proximal finger joints and metacarpophalangeal joints, and the joints are swollen and painful. However, rheumatoid joints are more prominent in the proximal joints and metacarpophalangeal joints, and the joints are swollen and painful. The synovial inflammation is much more pronounced in rheumatoid joints than in osteoarthritis.
Psoriatic arthritis is also prone to involve the distal finger joints but the x-ray performance is different from that of osteoarthritis. The patient has a psoriatic skin rash.
Pseudogout is a painful swelling of local joints (knee is most commonly involved) caused by calcium pyrophosphate crystals deposited in articular cartilage, synovial membrane, periosteum and ligaments. The latter two can be distinguished from osteoarthritis.
The disease is differentiated from hip tuberculosis and aseptic osteonecrosis according to the patient’s age, clinical manifestations and X-ray features.