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The first step is rest — stop all exacerbating activity in order to address your injury, at least for a few days or so. More rest (a few weeks) may be needed depending on the severity of your back injury. For a backache, laying on your back with your knees bent and legs slightly elevated is a good idea because it can take the pressure off the low back joints and provide some pain relief.  Laying on your back for hours at a time is not a good idea, either. Get up at least once an hour to move around even a little bit, and try going for a leisurely walk every day. Avoid excessive sitting (more than 30 minutes at a time) because it puts more pressure on the low back joints and may further irritate them. Cold therapy (ice wrapped in a thin towel or frozen gel packs) should be applied to the injury as soon as possible in order to stop reduce inflammation. Ice should be applied for 10 – 15 minutes every hour, then reduce the frequency as the pain and swelling subside. Compressing the ice against your back will help to further combat the inflammation.  Backaches from joint sprains are usually described as sharp and shooting in nature and they tend to be fairly debilitating. Most range of motion in the affected area is lost, and walking, sitting and sleeping are noticeably impaired. People with spinal joint sprains usually walk hunched over and to the side because the muscles surrounding the affected joints quickly spasm to "guard" the injury. Chiropractors and osteopaths are spinal specialists that focus on establishing normal motion and function of the small spinal joints that connect the vertebrae, called spinal facet joints. Manual joint manipulation, also called an adjustment, can be used to unjam or reposition facet joints that are slightly misaligned, which triggers inflammation and sharp pain, particularly with movement. You can often hear a "popping" sound with a spinal adjustment, similar in concept to when you extend your knuckles. Traction techniques or stretching of your spine may also help.  Although a single spinal adjustment can sometimes completely relieve your back sprain, more than likely it will take three to five treatments to notice significant results. If uneven leg lengths or flat feet is deemed to be the primary cause of your backache, then your doctor or chiropractor may recommend orthotics, which are custom made shoe inserts that support the arches, promote better biomechanics when running or walking, and help alleviate back pain. A facet joint injection involves real-time fluoroscopic (X-ray) guidance of a needle through the back muscles and into the inflamed or irritated spinal joint, followed by a release of an anesthetic and corticosteroid mixture, which quickly relieves both pain and inflammation at the site. Facet joint injections take 20 – 30 minutes to do and the results can last from a few weeks to a few months.  Facet joint injections are limited to three within a six-month time frame. The pain relief benefits from facet joint injections typically begin on the second or third day post treatment. Until that time frame, your backache may get a little worse.

Summary:
Reduce your activity level. Apply ice. See a chiropractor or osteopath. Get a facet joint injection.