Most people present to the office with back pain of an insidious nature, meaning they don't know how it started. In these instances, as a doctor we have to be sure the pain is originating from the back and that it is not some other condition masquerading as back pain. Once that's done, there are many reasons for back pain that suddenly or gradually appears. There are many more, but here are five:
Poor Ergonomics
The definition of ergonomics is "the science of equipment design intended to maximize productivity and minimize worker fatigue and discomfort". In theory this is nice, but in reality humans are not designed to do the same thing over and over every day, especially in a seated position. Hence, this is one of the most common hidden causes of back pain. 
Diagram via CoreConcepts Muskuloskeletal Health Group
When we talk about ergonomics we are generally referring to the set up of your work station (both at work and at home)and your ability to function in it without causing injury to your body. Lower back pain, neck pain and repetitive stress injuries to the wrists happen slowly over time. Our bodies change and respond according to the forces put on them. Sitting at a desk all day with improper ergonomics is like doing a bad exercise all day every day. Factor in a stressful work/life environment and you can see how back pain is the result.
Poor Posture
Poor posture is epidemic. Sedentary lifestyles, computers, video games, anxiety and spinal imbalances such as scoliosis can wreak havoc with posture.
Over time our brain begins to think the improper posture is normal, so anything different is perceived as abnormal. This is especially true when we begin postural correction techniques. According to Wolff's Law which states bones will remodel, thicken and actually change shape over time and permanently diminish the amount of postural correction possible.
Proper posture has a neurological and musculoskeletal component. This means that the brain and the body have to be communicating in order for the brain to know where the body is in space and for the body to send appropriate signals back to the brain. Spinal misalignments impair this feedback.
Stress
Stress is a vague term that means different things to different people. There are three primary types of stress, namely emotional, physical and physiological.
Emotional stress can come from work, family and personal issues. Physical stress can occur from poor ergonomics, poor spinal alignment, overuse and trauma to name a few. Physiological stress can be the result of smoking, poor diet and exposure to toxins.
The net effect is that our body is stuck in the fear mode and we are constantly in the state of fight or flight. To put it simply, in caveman days the dinosaur would come, the cave man (or woman:)) would perceive the threat and run, and then retreat to his/her cave to safety and relax. Today, the dinosaurs never go away and hence we are stuck in the fight or flight mode leading to chronic stress syndromes. For a more thorough explanation of the actual physiological explanation of stress, see my article "the true effects of stress"
Weighted Squats
We all love toned back and leg muscles and weighted squats are the go-to way to achieve this. However, the effects can be devastating if you suffer a disc injury.
Personal trainers and gym rats sometimes don't understand the damage that doing squats with a weighted bar on the shoulders can have, even if performed with perfect form. Remember, the body responds to the forces put upon it. The compressive forces of weights with a bar on the shoulders cause cumulative damage to the integrity of the disc which lead to herniations and degenerative changes over time, but very often suddenly. The long term health of the lumbar (lower back) spinal discs are at risk with squats performed with weights on the shoulders. The biggest, strongest weight lifters suffer this type of injury; so less professional weight lifters should be wary. This is one exercise that is not recommended for the health of your spine and discs.
Being a New Mom or Dad
New moms have a big struggle with the bodily changes that occur before, during and after pregnancy. The transition to motherhood involves complex physical and hormonal changes that last months after delivering a child. Back pain can occur at any point during this time. Not only has the body changed structurally and physiologically, but the increased demands of feeding, lifting, bending and carrying a baby that gets heavier every day can cause significant, sometimes debilitating back pain.
Back pain during this time is not restricted to new moms. Fathers also experience back pain as the result of lifting, carrying, bending and picking up/putting down a baby. I call this "Daddy-Back". Thankfully fathers today are involved in child care, but they do suffer the same types of pain syndromes as new mothers during this time.
Think Chiropractic!!
There are many causes of insidious lower back pain. The above five are among the most common. It is important to see your Doctor of Chiropractic for evaluation and treatment of your spinal condition. By modifying your activities and taking care of your spine with chiropractic care, you can maintain a healthy spine and a healthy life.