Knee Popping, a Numb Big Toe, a Throbbing Arm: 6 Joint and Nerve Symptoms Explained

Most joint and nerve symptoms start the same way: something feels off, you search it at 11pm, and half the results say it's nothing while the other half say see a surgeon. This guide covers six symptoms people search for constantly: what usually causes each one, and which signs mean you should get checked soon.

It's written for patients, not clinicians. It won't diagnose you, but it should help you work out what kind of problem you might be dealing with and what to ask when you see someone about it.

Quick guide: six symptoms at a glance

Knee popping after an injury: what that pop might mean

Plenty of knees pop. If yours has clicked on the stairs for years without pain or swelling, that's usually just gas bubbles or soft tissue sliding over bone, and doctors call it painless crepitus. It's common and mostly harmless.

A pop you hear or feel at the moment you get hurt is a different thing. It often means a structure inside the knee has been damaged, and the details around it tell you a lot.

The swelling clock

Pay attention to how quickly your knee swells. This is one of the most useful clues you have.

• Swelling within the first few hours usually means bleeding inside the joint. In sports injuries, a torn anterior cruciate ligament (ACL) is the most common cause. A dislocated kneecap or a fracture can do the same.

• Swelling that creeps in overnight or over a day or two is more typical of a meniscus tear, because the meniscus has a poor blood supply and the joint fills with fluid more slowly.

• Little or no swelling with pain on the inner side of the knee often points to a sprain of the medial collateral ligament (MCL).

The usual suspects

• ACL tear. Typically a pivot, sudden stop or awkward landing. People describe a loud pop and a knee that feels shifty or gives way afterwards. The American Academy of Orthopaedic Surgeons has a clear overview of ACL injuries.

• Meniscus tear. A twist on a bent knee. The giveaway is mechanical: catching, clicking with pain, or the knee locking so you can't straighten it fully.

• Kneecap (patellar) dislocation. The kneecap slips out to the side and usually pops back. It's more common in teenagers and people with loose joints.

• Cartilage or bone bruise. A hard impact can damage the smooth joint surface even when ligaments survive.

What to do in the first few days

Protect the knee, use ice for swelling, keep it raised, and use crutches if walking hurts. Gentle movement within a pain-free range helps more than keeping it rigid. Don't push through a knee that gives way.

When you need imaging

Emergency doctors often use a short checklist called the Ottawa knee rules to decide on an X-ray. You'd usually get one if you're 55 or older, can't bend the knee to 90 degrees, have tenderness right on the kneecap or the bony bump on the outer side below the knee, or couldn't take four steps both straight after the injury and when you're examined. An MRI is the usual next step if a ligament or meniscus tear is suspected and symptoms don't settle.

Why this matters years later

Long-term studies suggest roughly half of people who tear an ACL or meniscus show signs of knee arthritis 10 to 20 years later, with or without surgery. That's the main reason to take rehab seriously after the pain fades: strong thighs and a healthy weight take load off the joint for decades. If you're already there, our guide to knee osteoarthritis treatment options walks through what's available, and the knee pain score tool gives you a simple way to track symptoms over time.

Knee hyperflexion: when the knee bends too far

Hyperflexion means the knee is forced to bend further than it comfortably can. Most knees bend to roughly 135 to 150 degrees. Push past that with force behind it and the structures at the back of the knee get squeezed while those at the front get stretched.

People mix it up with hyperextension, which is the opposite: the knee bending backwards. Both hurt, but they damage different structures.

How it happens

• Falling onto a bent knee, especially with the foot pointed

• Deep squats under a heavy load

• Being tackled or landed on while the knee is folded underneath you

• Kneeling sports and jobs: catchers, wrestlers, tilers, gardeners

• Sitting back hard on your heels

What it can injure

• The back of the meniscus. Deep bending pinches the rear portion (the posterior horn), and tears there are a classic result. Expect pain at the back or inner side of the knee, worse when squatting.

• The posterior cruciate ligament (PCL). A fall onto a bent knee with the foot pointed drives the shin bone backwards. PCL injuries are often milder than ACL tears and many heal without surgery. The AAOS explains PCL injuries in plain language.

• The quadriceps or patellar tendon. The front of the knee is stretched hard, which can strain these tendons.

• Cartilage behind the kneecap. Repeated deep loading can irritate it, leading to pain on stairs and after sitting.

What helps

A mild hyperflexion strain usually settles within a few weeks with relative rest, ice, and avoiding deep bending. A physical therapist can then rebuild strength in the quads, hamstrings and hips. See someone if the knee locks, catches, swells repeatedly, or feels unstable, because those point to a structural tear rather than a strain. Our sports injuries guide lists the treatments clinics offer for these injuries and what the research says about each.

Loss of cervical lordosis: what "straightening of the neck" on your report means

Your neck normally curves gently forward, like a shallow letter C facing backwards. That curve is called cervical lordosis, and in many adults it measures somewhere around 20 to 40 degrees, although healthy necks vary a lot.

When a radiology report says "loss of cervical lordosis," "straightening of the cervical lordosis" or "reversal of the cervical lordosis," it means the curve looks flatter than usual, or bends the other way. Some people call a straight neck "military neck."

Is it serious?

Often, no, even though it sounds alarming on a report.

Studies of people with no neck pain regularly find straight or even reversed curves, and a meta-analysis of cervical lordosis in people without symptoms found a wide normal range. A review of its prognosis concluded that loss of lordosis by itself doesn't reliably predict how much pain someone will have or how they'll do. The finding also changes with position: tucking your chin slightly during the X-ray, or tight muscles guarding a sore neck, can flatten the curve on the day.

Treat it as one finding among several, not a diagnosis.

What can cause it

• Muscle spasm after a strain or whiplash, which pulls the neck straight

• Hours of forward-head posture at screens, on phones and on long drives

• Disc degeneration, where discs lose height and the spine's shape shifts

• A previous neck injury or surgery, including fusion

• How your head was positioned when the X-ray was taken

Symptoms people link to it

Neck stiffness, aching across the shoulders, headaches that start at the base of the skull, and reduced range of motion are the usual complaints. If you also have tingling, numbness or weakness in an arm, the more important question is whether a nerve is being pinched. That's covered in the throbbing arm section below.

What helps

• Physical therapy aimed at the deep neck flexors, the small muscles that support the curve from the front

• Chin tucks. Sit tall, glide your chin straight back as if making a double chin, and hold for five seconds. Ten reps, a few times a day.

• Raising your monitor so the top sits roughly at eye level, and lifting your phone instead of dropping your head

• A pillow that keeps your neck level with your body when you sleep on your side or back

• Getting up and moving every 30 to 45 minutes at a desk

Some chiropractors and therapists use extension traction to try to restore the curve. A few studies report measurable change, but the evidence is modest, and pain relief doesn't always track with the X-ray angle. Surgery is rarely considered for the curve alone. It's mainly for people with progressive nerve or spinal cord compression.

For a wider look at neck and back problems and the treatments clinics offer, see our back and spine guide. If your report also mentions spinal stenosis or a thickened ligament, our explainer on the ligamentum flavum helps decode it.

Why is my arm throbbing?

Start with the urgent possibility. If the throbbing or aching is in your arm (especially the left) and comes with chest pressure, shortness of breath, sweating, nausea, or pain moving to your jaw or back, call 911. Heart attacks don't always look like they do in films, particularly in women.

Once that's ruled out, most throbbing arms come from a handful of sources, and where you feel it narrows things down fast.

Where it hurts and what it suggests

A pinched nerve in the neck

This is one of the most common reasons for a deep, throbbing or burning arm. A disc bulge or bony narrowing irritates a nerve root as it leaves the spine, and pain travels along that nerve's path. The fingers involved hint at which level: the thumb side often links to C6, the middle finger to C7, and the little finger side to C8. Turning your head or looking up may make it worse. The AAOS overview of cervical radiculopathy is a good primer. Most cases improve within a few weeks to a few months with physical therapy, adjusting activity and medication.

Shoulder and elbow tendons

The rotator cuff refers pain down to the outer upper arm, so a "throbbing arm" is often really a shoulder problem. Night pain and pain lifting your arm sideways are typical. Our rotator cuff and shoulder guide covers the treatments people usually try. Tennis and golfer's elbow cause a throbbing ache near the elbow after gripping, typing or lifting.

Other causes worth knowing

• Overuse or a new workout. Delayed muscle soreness peaks a day or two after unfamiliar exercise and fades within a few days.

• Thoracic outlet syndrome. Nerves or vessels get squeezed between the collarbone and first rib, causing aching, tingling and fatigue when your arm is raised.

• Peripheral nerve problems. Diabetes and other conditions can affect the arms as well as the feet. Our neuropathy guide explains the bigger picture.

• Infection. A red, hot, spreading area with fever needs prompt medical care.

Numb big toe: the back, the foot, or something else?

The cause of a numb big toe can sit anywhere between your shoelaces and your lower spine. Which part of the toe is numb, and whether the other foot is affected, usually tells you which.

Start with your shoes

Shoes are the usual culprit. Tight toe boxes, stiff hiking or ski boots, cycling shoes and laces pulled tight across the top of the foot can all compress the small nerves running to the big toe. Runners and hikers often notice the inner edge or tip of the big toe going numb after long outings. It usually comes back within hours to weeks once the pressure stops, though a badly irritated nerve can take longer.

Try a wider toe box, loosen or re-lace across the top of the foot, and check whether socks are bunching. If the numbness only shows up in certain shoes, that's your answer.

Bunions and a stiff big toe joint

A bunion pushes the joint outward, where it rubs against shoes and can irritate the nerve along the inner side of the toe. A stiff, arthritic big toe joint (hallux rigidus) can do something similar through bone spurs. Both tend to come with a visible bump or a joint that won't bend much.

Your lower back

The L5 nerve root, which exits the spine low in the back, supplies sensation to the top of the foot and the big toe. A disc herniation or narrowing at the L4-L5 level can make the big toe go numb even if your back barely hurts. Clues that the back is involved:

• Pain or tingling running down the outside of the leg or shin

• Weakness lifting the big toe or the front of the foot (foot slapping or tripping)

• Symptoms that change with sitting, bending or walking

Weakness lifting the foot, called foot drop, should be checked promptly. Our back and spine guide covers the conditions involved.

The nerve on top of the foot

Numbness specifically in the web space between the big toe and second toe often points to the deep peroneal nerve, which can be compressed on top of the foot by tight laces, boots or bony spurs.

Peripheral neuropathy

When numbness starts in the toes of both feet and creeps upward over months, peripheral neuropathy is high on the list. Diabetes is the most common cause, followed by vitamin B12 deficiency, heavy alcohol use, some chemotherapy drugs, thyroid problems and kidney disease. A simple blood test for blood sugar (HbA1c) and B12 is a sensible first step. MedlinePlus has a solid overview of peripheral nerve disorders, and our neuropathy page and diabetes page explain how clinics approach these conditions.

If you have diabetes and reduced feeling in your feet, check them daily for cuts or blisters you may not feel.

Circulation

Peripheral artery disease and Raynaud's phenomenon reduce blood flow to the toes. Look for cold, pale or purplish toes, cramping calf pain when walking that eases with rest, or color changes in the cold.

Can a numb big toe be reversed?

It depends on the cause. Pressure from shoes usually resolves. Nerve root compression often improves as the disc settles or with treatment. Neuropathy is harder, and the main goal is stopping it getting worse by treating the cause. The sooner the cause is found, the better the odds.

Ankle sore after walking

An ankle that aches after a walk, a long day on your feet, or a new step-count goal is usually telling you a tendon or joint is being loaded more than it can currently handle. Where it's sore tells you which.

Back of the ankle

This usually means Achilles tendinopathy. The tendon is stiff and sore first thing in the morning, warms up a little, then aches again later. It's common after a jump in walking or running distance, a change to flatter shoes, or with tight calves. The AAOS page on Achilles tendinitis covers the basics. Slow, progressive calf strengthening (heel raises) has some of the best evidence of any treatment for it.

Inside of the ankle

Pain behind the inner ankle bone, especially with an arch that seems to be flattening, suggests the posterior tibial tendon. This tendon holds up your arch, and when it weakens the foot gradually flattens. Caught early, it usually responds to bracing and exercises. Left alone, it can end in surgery. The AAOS explains adult-acquired flatfoot, which is where this can lead.

Outside of the ankle

Soreness on the outer side often comes from the peroneal tendons, or from leftover damage after a previous sprain. If your ankle rolls easily or feels wobbly on uneven ground, you may have chronic ankle instability, which responds well to balance and strength training.

Front of the ankle, or deep inside the joint

Pinching at the front when you walk uphill or squat can be anterior impingement from bone spurs. A deep, aching, stiff ankle may be arthritis. Unlike knee and hip arthritis, most ankle arthritis follows an old injury, such as a fracture or repeated bad sprains. Our joint pain guide covers treatment options for arthritic joints beyond the knee and hip.

Pinpoint bone pain

If one small spot on a bone hurts to press, especially after you've increased your activity quickly, think stress fracture. Stop the activity and get it checked, because walking through it can turn a small crack into a bigger problem.

What helps most ankles

• Cut back walking distance by a third to a half for a week or two, then build back up gradually

• Supportive shoes with a slight heel-to-toe drop if your Achilles is sore

• Calf raises, single-leg balance work and ankle strengthening

• Ice after activity for a flare, and anti-inflammatory medication if your doctor says it's safe for you

• A podiatrist or physical therapist if it isn't improving after four to six weeks

Ankles that are swollen, red and hot without an injury can mean gout or an inflammatory arthritis such as rheumatoid arthritis. Those need a doctor, not a rest week.

Where regenerative treatments fit, and where they don't

If a symptom on this list has been with you for months, you may have seen clinics offering platelet-rich plasma (PRP) or stem cell injections. Some of these treatments have real research behind them for specific problems. Others are being sold well ahead of the evidence. Here's where the evidence stands as of 2026.

Before you book anything:

• In the US, no stem cell product is FDA-approved for orthopedic conditions like arthritis, tendon injuries or back pain. Clinics offering them are operating outside approved uses.

• PRP and stem cells are different treatments. Our comparison of stem cells vs PRP explains how they differ, and the PRP treatment page covers what to expect.

• Prices vary widely for treatments that sound identical. Our guide on how much stem cell injections cost breaks down why, and the cost calculator gives you a ballpark.

• Know the red flags. Read our list of warning signs a stem cell clinic may not be trustworthy before any consultation.

If you're wondering whether you'd even be a reasonable candidate, the candidacy checker asks the screening questions a careful clinic would ask, and the clinic match quiz narrows down clinics by condition and location. You can also browse our regenerative orthopedics listings to see who treats joint and spine problems.

How to describe your symptom so a doctor can help

A ten-minute appointment goes further if you arrive with specifics. Write down:

• When it started, and whether there was a specific moment like a pop, a fall or a new activity

• Exactly where you feel it. If you can point to it with one finger, say so.

• What it feels like: throbbing, burning, sharp, aching, numb, or pins and needles

• What makes it better or worse, such as sitting, walking, stairs, turning your head, certain shoes, or time of day

• Anything else going on with it: swelling, locking, giving way, weakness, color change

• What you've already tried and whether it helped

• Any X-ray or MRI reports. Bring the actual wording, not your memory of it.

If you're seeing a regenerative medicine clinic, our article on what to expect at your first consultation and our checklist for choosing a stem cell doctor will help you get more out of it.

Frequently asked questions

Is knee popping after an injury serious?

It can be. A pop at the moment of injury followed by quick swelling, instability or locking often means a ligament or meniscus tear, and it should be examined. Painless popping that has been there for years, with no swelling, is usually harmless.

Can loss of cervical lordosis be corrected?

Sometimes the curve changes with physical therapy, posture work or traction, but the evidence for permanently restoring it is limited. More importantly, the curve itself doesn't reliably predict pain, so treatment usually focuses on symptoms, strength and movement rather than the X-ray angle.

Does a numb big toe mean diabetes?

Not necessarily. Tight shoes and a pinched nerve in the low back are common causes. Diabetes is more likely when the numbness affects both feet, started gradually, and is slowly spreading upward. A blood sugar test can rule it in or out.

Can tight shoes cause big toe numbness?

Yes, and it's one of the most common causes. Narrow toe boxes, stiff boots and tight laces can compress the small nerves to the big toe. The numbness usually fades once the pressure is removed, though it can take weeks if the nerve was irritated for a long time.

Why does my arm throb at night?

Rotator cuff problems and carpal tunnel syndrome are the classic night-time culprits, because lying on the shoulder or bending the wrist during sleep increases pressure. A pinched nerve in the neck can also flare when you lie in certain positions.

Why do my ankles hurt after walking all day?

Usually tendon overload, flat or unsupportive shoes, or early arthritis from an old injury. If the pain is behind the ankle, think Achilles. On the inner side, the posterior tibial tendon. On the outer side, the peroneal tendons or an old sprain.

What is the difference between knee hyperflexion and hyperextension?

Hyperflexion is the knee bending too far, which tends to injure the back of the meniscus, the PCL and the tendons at the front. Hyperextension is the knee bending backwards, which more often strains the ACL, the back of the joint capsule and the hamstrings.

Related reading

• Can stem cell therapy help with knee pain and joint arthritis?

• Stem cell therapy for knee pain: what to actually look for in a clinic

• Is stem cell therapy safe for arthritis?

• Stem cell therapy for hip arthritis

• How long do stem cells take to work?

• PRP therapy vs stem cell therapy

• Back pain disability score

This article is for general education and isn't a substitute for an examination by a qualified clinician. If your symptoms are severe, sudden or getting worse, see a doctor.