Individuals with Knee Osteoarthritis and Osteoporosis Represent a Distinctive Subgroup Whose Symptoms Originate from Differences in Subchondral Bone Rather than Cartilage

To explore the hypothesis that knee osteoarthritis patients with osteoporosis represent a sub-cohort with different disease characteristics and origin of symptoms. Men and women in the Osteoarthritis Initiative (OAI) at visit 5 (36 months) were examined for osteoporosis ( N = 1483) using DXA (T-score at femoral neck ≤ −2.5), use of bisphosphonates, or having experienced a fracture. Those with and without osteoporosis were compared by subchondral bone quality, bone marrow lesion (BML) properties, and cartilage thickness from MRI, with general linear modeling. Relationships between symptoms (12 months later) and each of cartilage or subchondral bone features were examined conditional on osteoporosis status. Overall, 15.2% of 1246 participants (825 women, 658 men, mean age: 64.4 ± 8.9yrs, BMI: 30.1 ± 4.9 kg/m 2 ) with knee OA likely had osteoporosis and showed lower medial and lateral subchondral bone density, smaller trabecular number and larger trabecular separation (all p