A 62-year-old woman from Delhi presents with a 3-year history of progressive pain and stiffness in both knees, worse in the morning and after prolonged sitting. She has a BMI of 28 kg/m². On examination, there is crepitus on knee flexion-extension, mild swelling, and reduced range of motion. X-ray of both knees shows joint space narrowing, osteophytes at the joint margins, and subchondral sclerosis. She denies any history of trauma or inflammatory arthritis. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Osteoarthritis of the Knee ### Key Clinical Features **Key Point:** The combination of insidious onset, mechanical symptoms (crepitus), morning stiffness that improves with activity, and radiographic evidence of degenerative changes (joint space narrowing, osteophytes, subchondral sclerosis) is pathognomonic for osteoarthritis (OA). ### Radiographic Hallmarks (Kellgren-Lawrence Grading) The patient's X-ray findings represent the classic degenerative pattern: | Feature | Osteoarthritis | Rheumatoid Arthritis | |---------|-----------------|----------------------| | Joint space | Narrowing (asymmetric) | Uniform narrowing | | Osteophytes | Present at margins | Absent | | Subchondral sclerosis | Yes | No | | Bone erosions | Minimal, marginal | Central, severe | | Soft tissue swelling | Mild | Marked | | Symmetry | Often asymmetric | Symmetric | ### Why Osteoarthritis? 1. **Age and BMI:** OA is a disease of aging and mechanical overload; this patient's age (62) and overweight status (BMI 28) are classic risk factors. 2. **Mechanical symptoms:** Crepitus, pain worse with activity and after rest, morning stiffness that improves with movement—all typical of OA. 3. **Radiographic signature:** Osteophytes and subchondral sclerosis are the hallmark degenerative changes, NOT seen in inflammatory arthritis. 4. **Negative inflammatory history:** No systemic symptoms, no polyarticular involvement pattern typical of RA. **High-Yield:** Morning stiffness in OA is typically <30 minutes and improves with activity; in RA it lasts >1 hour and worsens with activity. ### Pathophysiology **Clinical Pearl:** OA is a degenerative joint disease characterized by progressive loss of articular cartilage, with secondary bone remodeling (osteophyte formation) and subchondral bone changes. It is NOT primarily an inflammatory condition, though low-grade inflammation does occur. **Mnemonic: LOSS** — Loss of cartilage, Osteophytes, Subchondral sclerosis, Stiffness (mechanical). ### Management Approach ```mermaid flowchart TD A[Osteoarthritis diagnosis confirmed]:::outcome --> B[Weight management + physiotherapy]:::action B --> C{Pain control adequate?}:::decision C -->|Yes| D[Continue conservative management]:::action C -->|No| E[Intra-articular corticosteroid injection]:::action E --> F{Symptom relief?}:::decision F -->|Yes| G[Repeat every 3-6 months]:::action F -->|No| H[Consider total knee replacement]:::action ``` **Key Point:** First-line management is always conservative: weight loss, activity modification, physiotherapy, and NSAIDs. Intra-articular steroid injections are second-line; joint replacement is reserved for end-stage disease.