In short
Difficulty climbing stairs, rising from a chair or getting up off the floor is muscle weakness, not back pain. When it affects both legs, builds over weeks and sits in the thighs and hips rather than travelling down a nerve, the problem is often in the muscle itself — and that is a different specialty from the spine.
Search for weak legs and almost everything returned is about the spine — discs, nerves, sciatica, cervical or lumbar compression. That is where most people are sent, and for many it is right.
But there is a pattern that is not the spine at all, and it is regularly missed for months because nobody asks the right question. The question is not where does it hurt. It is what can you no longer do.
Weakness is not pain
This distinction does most of the diagnostic work.
Weakness means the muscle cannot generate the force. You can no longer rise from a low chair without pushing with your arms. Stairs require the banister. Getting off the floor after sitting cross-legged — a daily movement in most Indian homes — becomes a production. Hanging washing or combing hair becomes tiring if the arms are involved too.
Pain limits what you do because it hurts, but the strength is there if you push through.
People routinely describe weakness as pain, because the experience is of struggling. A doctor who takes "my legs hurt" at face value and orders a lumbar MRI will find age-related changes — because almost everyone has them — and the real problem continues.
The pattern that points at muscle
Muscle disease has a signature:
- Both sides, roughly equally. Not one leg.
- Proximal — hips and thighs, shoulders and upper arms. The muscles close to the trunk. Grip strength is usually preserved early, which is why people can still open a jar but cannot climb stairs.
- Builds over weeks to months, rather than appearing overnight or after an injury.
- No numbness or tingling. Nerve compression causes sensory symptoms; muscle disease does not.
- Sometimes difficulty swallowing, or the voice changing — the swallowing muscles can be involved, and this is important to mention.
Compare that with a nerve problem: usually one leg, pain travelling in a line down the limb, numbness or pins and needles in a defined area, often worse on certain movements of the spine.
What causes proximal weakness
Several things, and they are not all rheumatological.
Inflammatory muscle disease (myositis). The immune system attacks muscle. This includes polymyositis, dermatomyositis — which adds a characteristic rash on the eyelids, knuckles and upper chest — and immune-mediated necrotizing myopathy. These are treatable, and treated earlier they do better.
Statin-related muscle problems. Common and important. Most statin muscle symptoms are aches that settle on stopping. A small number develop a genuine immune-mediated myopathy that continues after the statin is stopped and needs immunosuppressive treatment. Anyone on a statin with progressive weakness needs a CPK checked.
Thyroid disease. Both an underactive and an overactive thyroid cause proximal weakness, and it reverses when the thyroid is corrected. Covered in thyroid trouble and aching joints.
Vitamin D deficiency. Severe, long-standing deficiency causes a proximal myopathy with a waddling gait and bone pain. Common here, and genuinely treatable — see what vitamin D deficiency explains.
Steroids themselves. Long-term steroid treatment causes a proximal myopathy, which is awkward when steroids are also the treatment for myositis. The CPK is typically normal in steroid myopathy, which helps distinguish it.
Other causes include low potassium, some infections, inherited muscular dystrophies presenting in adulthood, and rarely a muscle problem associated with an underlying cancer.
The test that opens the question
Creatine kinase (CPK or CK) is an enzyme released when muscle is damaged. In active inflammatory muscle disease it is often substantially raised — sometimes many times the upper limit.
It is a simple, cheap blood test, and it is very often not ordered, because the complaint was recorded as pain rather than weakness.
Two cautions. A raised CPK is not specific: vigorous exercise in the days before, an intramuscular injection, and some ethnic variation all raise it modestly. And a normal CPK does not completely exclude muscle disease, particularly in long-standing dermatomyositis.
If the CPK is raised and weakness is real, what follows is usually:
- Myositis-specific antibodies, which help classify the type and predict complications such as lung involvement
- MRI of the thigh muscles, showing inflammation and indicating where to biopsy
- EMG, distinguishing muscle from nerve
- A muscle biopsy, where the diagnosis needs to be certain before long immunosuppression — nerve and muscle biopsy explains what that involves
- Screening for lung involvement, since interstitial lung disease can accompany myositis — see autoimmune interstitial lung disease
- Age-appropriate cancer screening, because some myositis, particularly dermatomyositis in adults, is associated with an underlying malignancy
What to tell your doctor
Be concrete about function. These sentences get the right test ordered:
- "I cannot get up from the floor without holding something."
- "I push with my arms to get out of a chair."
- "I need the banister on stairs now and I did not six months ago."
- "I cannot hold my arms up long enough to comb my hair."
- "I have started coughing when I drink water." — mention this one early.
And mention every medicine, particularly statins, and any rash, however trivial it seems. A faint purple discolouration over the eyelids or scaly patches over the knuckles changes the diagnosis entirely.
When it is urgent
- Weakness that is worsening over days rather than months
- Any difficulty swallowing, choking or nasal regurgitation
- Breathlessness alongside the weakness
- Very dark, cola-coloured urine with muscle pain, which can mean muscle breakdown and kidney risk
These need assessing immediately rather than at the next available appointment.
What treatment involves
For inflammatory muscle disease the principle is to suppress the inflammation quickly, then move off steroids onto something that can be taken long term.
Treatment usually begins with steroids at a substantial dose, because they work fast and muscle that stays inflamed is muscle that is lost. Alongside, a steroid-sparing drug — methotrexate, azathioprine or mycophenolate — is started, because it takes weeks to months to work and the steroid dose is reduced as it takes over.
Progress is followed by strength rather than by the CPK alone: can you rise from a chair, climb stairs, lift your arms? A falling CPK with no improvement in function is not success.
Physiotherapy matters more than people expect. Muscle that has been inflamed and then rested wastes, and strength has to be rebuilt deliberately once the inflammation is controlled.
The point of catching it
Inflammatory muscle disease responds to treatment, and the muscle that has been lost recovers less completely the longer it has been inflamed. A thyroid problem reverses with a tablet. A statin myopathy stops progressing when the drug is stopped.
All of them require that somebody first recognised the complaint as weakness, and checked a CPK. If you are struggling with stairs and the floor, and the only test you have had is a scan of your spine, that is worth an assessment.
Common questions
What causes muscle weakness in both legs?
When weakness affects both legs, sits in the hips and thighs, and builds over weeks, common causes are inflammatory muscle disease, thyroid disease, severe vitamin D deficiency, statin-related muscle problems and long-term steroid use. A spine problem more typically affects one leg and comes with numbness or pain travelling down the limb.
How do I know if it is muscle or nerve?
Muscle disease causes weakness on both sides, close to the trunk, without numbness or tingling. Nerve compression usually affects one limb, follows a line, and causes sensory symptoms in a defined area. Difficulty rising from the floor or a chair with no numbness points towards muscle.
What does a high CPK mean?
It means muscle is being damaged. In inflammatory muscle disease it is often substantially raised. It is not specific — hard exercise in the preceding days and intramuscular injections raise it modestly — and a normal result does not completely exclude muscle disease, particularly in long-standing dermatomyositis.
Can statins cause muscle weakness?
Yes. Most statin muscle symptoms are aches that settle after stopping. A small number of people develop an immune-mediated myopathy that continues after the statin is stopped and needs immunosuppressive treatment. Progressive weakness on a statin should prompt a CPK test rather than simply pushing on.
When is leg weakness an emergency?
When it worsens over days rather than months, when there is difficulty swallowing or choking, when there is breathlessness alongside it, or when urine turns dark and cola-coloured with muscle pain. Each of those needs assessing immediately.
Sources
- MedlinePlus — myositis medlineplus.gov
- MedlinePlus — creatine kinase test medlineplus.gov
- NHS — underactive thyroid www.nhs.uk
- NHS — vitamin D www.nhs.uk
This article is general information and does not replace a consultation.