Knee osteoarthritis (KOA) is a chronic bone and joint disease caused by cartilage degeneration and bone hyperplasia of the knee joint.
Clinical manifestations: Knee pain, which usually occurs in the morning, is relieved by exertion, but may worsen if there is too much activity. Joint swelling, fluid accumulation, and varying degrees of dysfunction seriously affect the quality of life of patients.
Diagnosis: clinical symptoms, signs, history, plus imaging.
Clinical staging: Clinically, according to the location of the lesion, KOA is divided into patellofemoral joint type, intercondylar type, tibiofemoral joint type, mixed type, etc.
China's "Knee Osteoarthritis Ladder** Expert Consensus, 2019", based on clinical symptoms and signs, combined with imaging examination, divided KOA into early, early, intermediate and late stages.
1. Initial stage. Pain, occasional knee pain.
activities, which can carry out normal daily activities.
Swelling, no swelling of the knee joint.
Malformation, no obvious deformity ( or pre-existing deformity).
X-rays show suspicious narrowing of the joint space, and osteophytes may be present.
2. Early. Pain, often knee pain.
Activity, daily activities are basically not affected, a small number of patients walk on flat roads are occasionally affected, often pain when standing up, squatting or going up and down stairs, and slight limitation of activities.
Swelling, occasional swelling;Malformation, no obvious deformity ( or pre-existing deformity).
X-rays show mild narrowing of the joint space with significant small osteophytes.
3. Medium-term. Pain, often severe pain in the knee joint.
Activity, where daily activities are limited because of pain.
Swelling, ** swelling of the knee joint.
Deformity, which may be marked with mild varus or valgus deformity of the knee.
X-rays show clear joint space narrowing, moderate osteophytes, mild sclerosis of subchondral bone, and possible bony deformities of the knee (see Varus, Valgus, Flexion).
4.Advanced.
Pain, knee pain is very severe.
Activities, severe restrictions on daily activities.
Swelling, which may often occur in the knee joint.
Deformity, which may be severe varus, valgus, or flexion contracture deformity.
X-rays show severe joint space narrowing, massive osteophyte formation, marked subchondral osteosclerosis, and significant bony deformity of the knee.
Imaging Methods:
Plain radiograph: Knee x-ray includes anteroposterior and lateral radiographs in weight-bearing position, and axial radiographs of the patella. X-rays show narrowing of the joint space, osteophyte formation at the articular margins, subchondral osteosclerosis, and cystic changes.
CT scan: CT scans have also increased in recent years, making it easier to observe whether there is more fluid in the joint cavity and bursa to rule out other joint diseases. Post-processing, 3D or multi-plane reconstruction can be performed.
MRI Examination:
At present, MRI is considered to be the best way to show osteoarthritis, which can not only observe bone hyperplasia, cystic changes, etc., but also observe and grade cartilage lesions, as well as tendons, ligaments, surrounding soft tissues and other lesions.
X-ray indexing of knee osteoarthritis.
At present, there are no accepted criteria for the grading and staging of osteoarthritis on CT MR. In clinical practice, the traditional X-ray indexing standard is still used.
The X-ray indexing method, based on the pathological evolution process of osteoarthritis, has different X-ray manifestations at different stages, which provides a reference for clinical indexing.
d**id indexing method.
Articular surface is smooth, joint space is normal, suspicious marginal bone hyperplasia, I degree.
Holden indexing grade: mild narrowing of the joint space, small osteophyte formation, and slight sclerosis Grade: moderate narrowing of the joint space, moderate bone spur formation, and moderate sclerosis Grade: Bone to bone changes with hardening but no bone loss Grade: Severe sclerosis with loss of joint space. 
Lamiform changes at the margins of the patella and medial femoral condyles with sclerotic bone-to-bone changes but no bone loss, third-degree.
Kellgren-Lawrence indexing
Grade 0, normal knee joint, smooth articular surface, uniform and symmetrical space, no bone hyperplasia or sclerosis is seen.
Formation of large osteophytes, uneven articular space, severe medial stenosis, and uneven articular surface, grade IV.