A 45-year-old male presents with progressive left knee pain and varus deformity. An AP weight-bearing radiograph of the knee is obtained. The structure marked **C** (intercondylar notch and tibial spines) is examined. Which of the following radiographic findings in the medial compartment would be MOST consistent with primary osteoarthritis of the knee, and what would be the expected appearance at the intercondylar region?

Explanation

## Why "Medial joint space narrowing with osteophytes and sclerosis; intercondylar notch remains unaffected" is right Medial compartment osteoarthritis is the most common pattern of primary knee OA in Indians, presenting with progressive medial joint space narrowing, osteophyte formation, and subchondral sclerosis. The intercondylar notch and tibial spines (marked **C**) are NOT directly involved in the degenerative process of medial compartment OA — they remain radiographically normal. This is the classic Kellgren-Lawrence grading pattern for unicompartmental medial OA, which is amenable to unicompartmental knee replacement in younger, active patients. Weight-bearing AP views are most sensitive for detecting this medial-predominant narrowing. (Maheshwari Orthopedics 10e — AP Knee Joint Space Assessment; KL Grading I–IV) ## Why each distractor is wrong - **Lateral joint space narrowing predominantly; intercondylar notch shows early erosive changes**: Lateral compartment OA is less common as a primary presentation in Indians; erosive changes at the intercondylar notch are NOT a feature of primary OA and would suggest inflammatory or erosive arthropathy (e.g., rheumatoid arthritis). - **Uniform joint space loss bilaterally with tibial spine flattening**: Bicompartmental or tricompartmental OA may show uniform loss, but tibial spine flattening is not a hallmark of primary OA and would raise suspicion for inflammatory or post-traumatic changes. - **Intercondylar notch widening with lateral tibial rim avulsion fracture**: Intercondylar notch widening and Segond fracture (lateral tibial rim avulsion) are pathognomonic of ACL injury, NOT osteoarthritis. This is a secondary sign of ligamentous injury, not degenerative joint disease. **High-Yield:** Medial compartment OA > lateral in primary knee OA; intercondylar notch remains normal; weight-bearing views best reveal medial joint space narrowing. [cite: Maheshwari Orthopedics 10e — AP Knee Joint Space Assessment; Kellgren-Lawrence Grading]