joints of free lower limb

例句：

1. 1. The doctor examined the patient's joints carefully.
   医生仔细检查了病人的关节。
2. 2. Joints are important for movement and balance.
   关节对于运动和平衡至关重要。
3. 3. The scientist discovered new ways to treat arthritis.
   科学家发现了治疗关节炎的新方法。