What the criteria ask for at each level

DC 5235–5243 — 38 CFR §4.71a (General Rating Formula for the Spine)

Rating	What the record has to show
10%	Forward flexion >60° but ≤85°, OR muscle spasm/guarding/tenderness not causing abnormal gait.
20%	Forward flexion >30° but ≤60°, OR muscle spasm/guarding severe enough to cause abnormal gait or spinal contour.
40%	Forward flexion 30° or less, or favorable ankylosis of the entire thoracolumbar spine.
50%	Unfavorable ankylosis (fixed stiffness) of the entire thoracolumbar spine.
10–60% (IVDS)	Alternative formula: weeks of physician-prescribed bed rest in the past year (60% requires 6+ weeks).

The schedule's own words

Ratings turn on specific terms, and a record that describes the same reality in different language often reads as a lower rating. These are the words this code measures:

forward flexion
muscle spasm and guarding
abnormal gait
flare-ups
incapacitating episodes requiring physician-prescribed bed rest

Evidence that moves this rating

Range-of-motion measurements in degrees (the examiner MUST use a goniometer)
MRI/X-ray showing disc or degenerative findings
A flare-up log: date, trigger, duration, what it stopped you from doing

What your statement has to cover

Doctors chart symptoms; they rarely chart consequences. That part is yours, and it is usually what separates a documented rating from a reported one.

Describe flare-ups: how often, how long, and what you cannot do during them.
Describe how pain changes your walk ("abnormal gait") — that alone can support 20%.
If a doctor has ever prescribed bed rest, say so with dates — it triggers the alternate IVDS formula.

What lower back can lead to11 documented pathways

A secondary claim runs through a condition the VA already accepts, so the argument about your service is already won. What is left is the medical link — and a nexus opinion has to name the mechanism, not just the pair.

Can lead to	The mechanism a nexus has to state
Urinary frequency / voiding dysfunction	Severe lumbar nerve compression (cauda equina involvement) causes bowel and bladder voiding dysfunction.
Erectile dysfunction / FSAD	Lumbar nerve compression and long-term pain medications cause erectile dysfunction.
Degenerative arthritis	Altered gait and biomechanical compensation stress other joints, accelerating arthritis.
GERD (acid reflux)	Long-term NSAID / pain-medication use for this condition damages the stomach lining and relaxes the esophageal sphincter — a well-established medication-side-effect pathway.
Radiculopathy / nerve pain	Nerve compression in the lower back radiates pain, numbness, or weakness down the legs (sciatica).
Knee condition	Altered gait from back pain places abnormal stress on the knees, accelerating wear.
Hip condition (bursitis, arthritis, limited motion)	Altered gait and uneven weight distribution place abnormal mechanical stress on the hips, causing bursitis or arthritis.
Ankle or foot condition (incl. flat feet, plantar fasciitis)	Altered gait and overcompensation change foot mechanics (e.g., plantar fasciitis).
Depression	Chronic pain and depression are bidirectional — pain causes depression, which amplifies pain.
Sleep apneavia weight gain	Chronic pain limits exercise and disrupts sleep; weight gain bridges to sleep apnea.
Insomnia	Chronic pain interrupts sleep architecture.

Before you spend money on this claim

VA ratings do not add. Each new rating applies only to the part of you the VA still counts as unimpaired, then rounds to the nearest ten — so from 70%, a new 10% condition leaves you at exactly 70% and changes your payment by nothing.

That does not make the claim worthless; it can still matter for TDIU, for SMC, or later when something else is added. But it is worth knowing before you pay for a nexus letter rather than after. Check what one more condition does at your rating — it takes a minute.