Which diagnosis is NOT a recognized cause of secondary knee osteoarthritis?

• A. Hypothyroidism
• B. Hyperparathyroidism
• C. Acromegaly
• D. Rickets

Answer: (A)

Secondary osteoarthritis arises when an underlying systemic condition alters joint loading, bone turnover, or cartilage health, leading to earlier or atypical degenerative changes in the knee. Among the listed disorders, acromegaly, hyperparathyroidism, and rickets each disrupt the knee joint in ways that promote OA: acromegaly increases growth hormone/IGF-1 effects on cartilage, producing abnormal joint surfaces and accelerated wear; hyperparathyroidism alters bone remodeling around the joint, changing subchondral bone and joint integrity; and rickets causes defective mineralization and skeletal deformities that shift knee alignment and increase abnormal loading. Hypothyroidism, while it can cause various systemic effects and nondegenerative joint symptoms, is not classically a recognized cause of secondary knee OA.