1.Symptoms and signs
Osteoarthritis mainly manifests as pain, swelling, morning stiffness, joint effusion and bony hypertrophy of the affected joints, which may be accompanied by bone rubbing sounds during activity, dysfunction or deformity.
(1) Joint pain and pressure pain The most common manifestation of this disease is localized pain and pressure pain in the joints. The weight-bearing joints and hands are most likely to be involved. It is usually mild or moderate intermittent pain in the early stage, which improves with rest and worsens with activity. There may be localized pressure pain in the joints, which is especially obvious when there is joint swelling.
(2) Swelling of the joint In the early stage, there is limited swelling around the joint, but as the disease progresses, there may be diffuse swelling of the joint, thickening of the bursa or joint effusion. In the later stage, bony swelling around the joint may be detected.
(3) Morning stiffness Patients may experience joint stiffness and adhesion in the morning, which may be relieved after activity. The duration of morning stiffness is relatively short, usually a few minutes to ten minutes, and rarely exceeds half an hour.
(4) Joint friction sounds are mainly seen in osteoarthritis of the knee joint. Due to the destruction of cartilage and roughness of the joint surface, there is a bone rubbing sound (sensation) and twisting sensation when the joint is moved, or accompanied by local pain in the joint.
2.Osteoarthritis in different parts of the body
(1) Hand The distal interphalangeal joint is most commonly involved, showing bony enlargement on both sides of the extensor side of the joint, called Hebden’s node. The proximal interphalangeal joint is called Bouchard’s node when it is present on the extensor side. It may be associated with mild localized erythema, pain, and tenderness of the nodes. The involvement of the first carpometacarpal joint may result in square hand deformity due to osteophytes at its base, and snake-like deformity due to finger joint hyperplasia and lateral subluxation.
(2) Knee Knee involvement is the most common in clinical practice. Risk factors include obesity, knee trauma, and meniscectomy. The main manifestation is knee pain, which is aggravated by activity and relieved by rest. Severe cases may present with inversion or valgus deformity of the knee.
(3) Hip The involvement of the hip joint is mostly characterized by localized intermittent dull pain, which may become persistent with the development of the disease. In some patients, the pain can radiate to the groin, inner thighs and buttocks. The hip joint movement is mostly limited by internal rotation and external rotation, followed by internal retraction, external rotation and extension.
(4) Spine Cervical spine involvement is more common. There may be hyperplasia and osteophytes of the vertebral body, intervertebral disc and posterior synovial joint, causing local pain and stiffness, and corresponding radiological pain and neurological symptoms when local blood vessels and nerves are compressed. Involvement of the cervical spine compresses the vertebrobasilar artery, causing symptoms of inadequate blood supply to the brain. Intermittent claudication and cauda equina syndrome may occur when lumbar spine osteophytes lead to spinal stenosis.
(5) Foot The metatarsophalangeal joint is often involved, and in addition to local pain, pressure pain and bony hypertrophy, deformities such as bunions can also occur.
3.Special types of osteoarthritis
(1) Primary generalized osteoarthritis The distal interphalangeal joint, proximal interphalangeal joint and the first carpometacarpal joint are the preferred sites. Knee, hip, metatarsophalangeal joints and spine may also be involved. Symptoms are episodic and may include effusion, redness and swelling of the involved joints. It can be divided into two categories based on clinical and epidemiological characteristics: (1) the nodular type, which mainly involves the distal interphalangeal joints, is more common in women and has family clusters. The non-nodular type is predominantly involved in the proximal interphalangeal joints and is not characterized by gender or family clustering, but often presents with recurrent peripheral arthritis. Severe patients may have increased sedimentation and increased C-reactive protein.
(2) Erosive inflammatory osteoarthritis is common in postmenopausal women, mainly involving the distal and proximal interphalangeal joints and carpometacarpal joints. There is a familial tendency and recurrent acute attacks. Pain and tenderness in the affected joints may eventually lead to deformity and ankylosis of the joint. The patient’s synovial examination reveals marked proliferative synovitis with immune complex deposition and vascular opacification. x-ray shows marked osteophytes and subchondral osteosclerosis, and in advanced stages, marked bone erosion and bony joint ankylosis.
(3) Diffuse idiopathic osteomalacia occurs in middle-aged and elderly men. The lesions involve the entire spine and show diffuse osteophytes with extensive hyperplastic ossification of the spinal ligaments and their adjacent osteo-cortical hyperplasia. However, the small vertebral joints and intervertebral discs remain intact. X-rays show characteristic calcification of the anterior and posterior longitudinal ligaments of the vertebral body, mainly in the lower thoracic segment, usually with 4 or more consecutive vertebrae, and may be accompanied by extensive osteophytes.
4.Laboratory tests
The indicators of routine blood, protein electrophoresis, immune complexes and serum complement are generally within normal range. Patients with synovitis may have mildly elevated C-reactive protein and blood sedimentation. Rheumatoid factor and antinuclear antibodies are negative. Patients with secondary osteoarthritis may present with abnormal laboratory tests of the primary disease.
Those who develop synovitis may have joint effusion. However, the joint fluid is generally clear, yellowish, and of normal or slightly reduced viscosity, but with good coagulation of mucin.
5.X-ray examination
The X-ray features of osteoarthritis are: asymmetric joint space narrowing; subchondral bone sclerosis and cystic changes; osteophytes and bone redundancy formation at the joint edges; intra-articular free bodies; joint deformation and subluxation. These changes are important for the diagnosis of osteoarthritis.