Knee
Knee Osteoarthritis
슬관절 골관절염
Cartilage degradation causing bone-on-bone friction, pain, and joint space loss
- How common
- Very Common (50+)
- Typical age
- Ages 50+
What is it?
Progressive articular cartilage degradation leads to joint space narrowing, subchondral bone exposure, osteophyte formation, and secondary synovitis.
Commonly affected: Medial compartment most commonly affected (75% of cases)
How it develops
- Cartilage BreakdownRepetitive loading damages chondrocytes and extracellular matrix
- Cartilage LossProgressive thinning and fibrillation of articular cartilage
- Osteophyte FormationMarginal osteophytes (bone spurs) form at joint margins
- Synovial InflammationCartilage debris irritates synovium, causing effusion and secondary synovitis
Symptoms
- Activity-Related Knee PainPain with weight-bearing; worse climbing/descending stairs and squatting
- Joint Effusion / SwellingKnee swelling from synovial effusion; warmth and stiffness
- Morning Stiffness (<30 min)Morning stiffness lasting <30 minutes (cf. >1 hour in RA)
- Deformity & InstabilityVarus deformity (bow-leg), giving way sensation
- CrepitusGrating sensation/sound with knee motion (bone-on-bone friction)
How it is examined
- Joint Line TendernessMaximal tenderness along the medial joint line
- Patella Grind TestGrinding patella against femoral condyle — crepitus and pain
- Ballottement TestFluid wave or patella tap indicates knee effusion
Imaging
Weight-bearing AP X-ray is essential. Kellgren-Lawrence grading based on 4 key findings.
- Medial joint space narrowing
- Subchondral sclerosis
- Osteophyte formation
- Subchondral cysts
MRI evaluates cartilage thickness, meniscal integrity, ligament status, and bone marrow edema.
- Cartilage defects/loss
- Meniscal degeneration/tear
- Bone marrow edema pattern
- Baker's cyst
Non-surgical care
- Weight Loss + ExerciseEach kg lost reduces knee load by ~4 kg; strengthening quadriceps protects joint
- NSAIDs + AcetaminophenFirst-line pharmacotherapy; topical NSAIDs minimize GI side effects
- Intra-articular InjectionsCorticosteroid injection for acute flares; hyaluronic acid for longer-term relief
- Physical Therapy + BracingQuad strengthening, lateral wedge insoles, unloader brace for varus OA
Conservative options are generally tried first. Medications listed here can have side effects — discuss them with your prescriber.
When surgery is considered
Severe pain/disability, failed 6+ months conservative care, end-stage joint space loss
Procedures that may be discussed
- Total Knee Arthroplasty (TKA) — gold standard
- Unicompartmental Knee Arthroplasty (UKA)
- High Tibial Osteotomy (HTO) for young varus OA
Outlook
TKA provides excellent outcomes — 95%+ satisfied; implants last 15–20+ years.