Image is from academic paper:
Three-dimensional ultrasonographic application for analyzing synovial hypotrophy of the knee in patients with osteoarthritis
Osteoarthritis: When cartilage on the ends of bones in joints gradually wears
away leading to pain, and stiffness (most often seen in hands, knees, hips and spine).
Common causes: Being overweight, injury, age
Treatment: There is no cure, so usually drugs (e.g., acetaminiphen, NSAIDs, or Narcotics), therapy or (cortisone shots) or surgery.