Intervertebral disc degeneration is one of the most common mechanical causes of low back pain, and it occurs when the usually rubbery discs lose integrity as a normal process of aging. In a healthy back, intervertebral discs provide height and allow bending, flexion, and torsion of the lower back. As the discs deteriorate, they lose their cushioning ability.
Tight hip flexors can result in lower back pain, hip pain and injury.  A lot of strain is put on those muscles during activities that involve sprinting and kicking.  For example, runners are more prone to hip flexor injuries because of the small, repetitive movement during running.   But even if you’re not an athlete, hip flexor injuries can occur during everyday activities (for instance, slipping and falling or running to catch a bus).  When those tight muscles are suddenly stretched beyond what they are accustomed to, you might also experience pain in the upper groin region, typically where the hip meets the pelvis.   
Back “spasms” are a largely a myth — there’s no such thing a sustained painful contractions of muscles in otherwise healthy people (see Cramps, Spasms, Tremors & Twitches) — but the kernel of truth in the idea of “spasms” may be the idea of trigger points, which are hypothetical “micro cramps,” tiny patches of painfully contracting muscle. Although this idea is controversial, it is nevertheless one of the most likely explanations for common aches and pains that mostly stick to one area (especially the back) and have no other obvious cause. See Back Pain & Trigger Points. BACK TO TEXT
Contour Sleep Knee Spacer: Correct sleep alignment is a critical component to rehabilitating an injured hip. This device can help to decrease pressure to the legs and hips while you sleep. Perfect for side sleepers, the Contour Sleep Knee Spacer fits softly between the knees without disrupting your sleep. It helps tense muscles relax and lets you have a better night’s sleep free from painful hip tension.

Strength training is another key part of the “do” category, Dr. Vasileff says. “It’s a good idea to focus on quad, hamstring, and glute strength,” he says. These muscles surround your hips and provide support, along with your core—which is another area to focus on. “Strengthening your core helps to normalize your walking pattern and stabilize how your pelvis and hips move,” Dr. Vasileff says. That translates to less pain and better hip mobility.
Sit on floor with knees bent and shins stacked with right leg on top. Use your hand to position right ankle on left knee. Ideally, the right knee will rest on the left thigh, but if your hips are tight, your right knee may point up toward the ceiling (overtime, as your hips become more open, your knee will lower). Keeping your hips squared to the front of the room, hinge at the hips and slowly walk hands slightly forward. If this is enough of a stretch, hold here, or fold your torso over your thighs to go deeper. Hold for at least 30 seconds, then repeat on opposite side.
Initial management with non–medication based treatments is recommended.[6] NSAIDs are recommended if these are not sufficiently effective.[6] Normal activity should be continued as much as the pain allows.[2] Medications are recommended for the duration that they are helpful.[13] A number of other options are available for those who do not improve with usual treatment. Opioids may be useful if simple pain medications are not enough, but they are not generally recommended due to side effects.[4][13] Surgery may be beneficial for those with disc-related chronic pain and disability or spinal stenosis.[14][15] No clear benefit has been found for other cases of non-specific low back pain.[14] Low back pain often affects mood, which may be improved by counseling or antidepressants.[13][16] Additionally, there are many alternative medicine therapies, including the Alexander technique and herbal remedies, but there is not enough evidence to recommend them confidently.[17] The evidence for chiropractic care[18] and spinal manipulation is mixed.[17][19][20][21]
Radiculopathy is a condition caused by compression, inflammation and/or injury to a spinal nerve root. Pressure on the nerve root results in pain, numbness, or a tingling sensation that travels or radiates to other areas of the body that are served by that nerve. Radiculopathy may occur when spinal stenosis or a herniated or ruptured disc compresses the nerve root.
Talmage, J; Belcourt, R; Galper, J; et al. (2011). "Low back disorders". In Kurt T. Hegmann. Occupational medicine practice guidelines : evaluation and management of common health problems and functional recovery in workers (3rd ed.). Elk Grove Village, IL: American College of Occupational and Environmental Medicine. pp. 336, 373, 376–377. ISBN 978-0615452272.
Some of these red flags are much less red than others, especially depending on the circumstances. For instance, “weight loss” is common and often the sign of successful diet! (Well, at least temporarily successful, anyway. 😃) Obviously, if you know of a harmless reason why you have a red flag symptom, it isn’t really a red flag (duh!). But every single actual red flag — in combination with severe low back pain that’s been going on for several weeks — is definitely a good reason to get yourself checked out.