This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Orthopaedics
Ahlback Grade2 changes of Osteoarthritis of the knee means: 
Select and explain. 
A. Joint space obliterated or almost obliterated, B. Minor bone attrition (<5 mm), C. Moderate bone attrition (5-15 mm), D. Severe bone attrition (>15 mm)
A: Joint space obliterated or almost obliterated
Answer: A: Joint space obliterated or almost obliterated 
Explanation: Ans. A. Joint space obliterated or almost obliteratedAhlback Radiographic Grading Scale of Osteoarthritis of the Tibiofemoral Joint:Grade of OsteoarthritisDescription0 =No radiographic findings of osteoarthritis1 =Joint space narrowing <3mm2 =Joint space obliterated or almost obliterated3 =Minor bone attrition (<5mm)4 =Moderate bone attrition (5-15mm)5 =Severe bone attrition (>15mm)