Some “natural” techniques can help ease pain, including acupuncture, yoga, tai chi and massage, government researchers said Thursday. A review of high-quality studies shows these approaches rarely cause any harm and can help people with lower back pain, headaches and arthritic knees, the team at the National Center for Complementary and Integrative Health found. They found evidence that: Acupuncture and yoga can help back pain Acupuncture and tai chi can help osteoarthritis of the knee…