🖐 Kellgren-Lawrence Radiographic OA Grading Simulator

Grade 0 — Radiographically Normal Knee Joint

No osteophytes, narrowing, or sclerosis are visible on plain film.

• None: Osteophytes (no marginal lipping)
• Normal: Joint space (~5.6mm medial)
• Absent: Sclerosis (no subchondral change)
• Baseline: Prevalence (reference population)

Defining the normal reference film

Short placeholder: normal films anchor the whole KL comparison scale.

Placeholder highlight: normal grade serves as the atlas baseline image.

Grade I — Doubtful Narrowing and Possible Osteophyte

Equivocal findings that may or may not represent early disease.

• Doubtful: Osteophytes (questionable lipping)
• ~4.6mm: Joint space (borderline)
• None: Sclerosis (not yet present)
• Low: Reader agreement (high inter-rater variance)

Why Grade I is the least reproducible category

Short placeholder: doubtful features drive most inter-reader disagreement.

Placeholder highlight: Grade I overlaps heavily with normal aging changes.

Grade II — Definite Osteophytes, Preserved Joint Space

Clear osteophyte formation marks definite radiographic osteoarthritis.

• Definite: Osteophytes (small marginal spurs)
• ~3.4mm: Joint space (possible narrowing)
• Minimal: Sclerosis (early subchondral change)
• Variable: Symptom link (often asymptomatic)

Osteophytes as the defining Grade II feature

Short placeholder: definite osteophytes are the diagnostic threshold for OA.

Placeholder highlight: Grade II is the minimum grade termed "definite OA".

Grade III — Moderate Narrowing with Subchondral Sclerosis

Multiple osteophytes and sclerosis accompany moderate joint narrowing.

• Multiple: Osteophytes (moderate size)
• ~2.0mm: Joint space (definite narrowing)
• Moderate: Sclerosis (subchondral whitening)
• Common: Symptoms (pain and stiffness)

Sclerosis emerges alongside cartilage loss

Short placeholder: sclerosis reflects bone remodeling under thinning cartilage.

Placeholder highlight: Grade III correlates strongly with clinical symptoms.

Grade IV — Severe Narrowing, Sclerosis, and Deformity

End-stage changes include bone-on-bone contact and joint deformity.

• Large: Osteophytes (severe marginal spurs)
• <1mm: Joint space (near-complete loss)
• Marked: Sclerosis (dense subchondral bone)
• TKA: Surgical (often indicated)

End-stage deformity and surgical thresholds

Short placeholder: deformity and bone-on-bone contact define Grade IV.

Placeholder highlight: Grade IV is the classic total knee arthroplasty indication.