If you can’t lift your foot upward at the ankle, the most likely explanation is a condition called foot drop. It happens when the muscles on the front of your shin that pull your foot up become weak or stop working, usually because a nerve supplying them is compressed or damaged. The two most common causes are a pinched nerve in the lower back (typically at the L4-L5 level) and compression of a nerve near the outside of the knee called the common fibular nerve.
Foot drop can come on suddenly or develop gradually, and it ranges from mild weakness to complete inability to lift the foot. Understanding what’s behind it helps you figure out how urgent the situation is and what to expect.
How the Nerve Pathway Works
Lifting your foot upward (called dorsiflexion) requires a chain of nerves that starts in your lower spine and travels all the way down your leg. Nerve roots from the L4 and L5 vertebrae feed into the sciatic nerve, which runs down the back of your thigh. Near the back of the knee, the sciatic nerve splits into two branches. The one that matters here is the common fibular nerve, which wraps around the bony bump on the outer side of your knee (the fibular head) before continuing down to the muscles in your shin.
At the fibular head, this nerve sits right under the skin with very little padding. That makes it the most frequently compressed single nerve in the leg. Any damage or pressure along this entire pathway, from the spine to the knee, can weaken or shut down the muscles that lift your foot.
Most Common Causes
L4-L5 radiculopathy, meaning a pinched nerve root in the lower back, is the most commonly recognized cause of foot drop. This usually happens when a herniated disc bulges into the spinal canal and presses on the nerve root, or when the bony opening the nerve passes through narrows (foraminal stenosis). You may also have lower back pain or pain shooting down the leg, but not always.
Compression of the fibular nerve at the knee is the next most common cause. This can happen from something as simple as habitually crossing your legs, sitting cross-legged on the floor for long periods, or wearing a tight cast or brace below the knee. People who are bedridden or who’ve recently had surgery and spent time with pressure on the outer knee are also at risk. Diabetes increases susceptibility because it makes nerves more vulnerable to compression injuries.
Less common causes include direct trauma to the nerve (a knee injury, a fracture near the fibular head), masses or cysts pressing on the nerve, inflammatory nerve conditions, and damage to the sciatic nerve higher up in the leg. Stroke and other brain or spinal cord conditions can also cause foot drop, though these are rarer and typically come with other neurological symptoms.
What It Feels Like Day to Day
The hallmark is difficulty pulling your toes and the front of your foot up toward your shin. You might notice your foot slapping the ground when you walk, or that you trip because your toes drag. Many people unconsciously compensate by lifting their knee higher than normal with each step, creating a distinctive “high-stepping” gait. You may also have trouble lifting your big toe or turning your foot outward.
Numbness or tingling often accompanies the weakness. With fibular nerve compression, the numb area is typically the top of the foot and the skin between the first and second toes. If the problem originates in the lower back, numbness may extend further up the leg or affect a broader area.
Red Flags That Need Emergency Care
Most foot drop is not an emergency, but certain combinations of symptoms signal a condition called cauda equina syndrome, where the bundle of nerves at the base of the spine is severely compressed. This requires immediate surgical treatment to prevent permanent damage. Go to an emergency room if your foot weakness occurs alongside any of the following: sudden difficulty controlling your bladder or bowels, numbness in the area where you’d sit on a saddle (inner thighs, buttocks, groin), or rapidly worsening weakness in both legs.
How Foot Drop Is Diagnosed
A doctor will test your ability to pull your foot upward against resistance, grade the strength of your shin muscles on a 0 to 5 scale, and check sensation on the top of your foot. They’ll likely watch you walk to see whether your foot clears the ground normally.
From there, imaging and electrical tests help pinpoint the cause. An MRI of the lower spine can reveal a herniated disc or narrowing around the nerve root. A nerve conduction study and electromyography (EMG) measure how well the nerve is transmitting signals and whether the muscles are responding, which helps distinguish between a spine problem and nerve compression at the knee.
Treatment Options
Bracing
An ankle-foot orthosis (AFO) is often the first practical step. This is a lightweight brace, usually made of plastic, that fits inside your shoe and holds your foot at a neutral angle so it doesn’t drop during walking. There are two main types. A solid AFO completely limits ankle movement and is used when both the muscles that lift the foot and those that push off are weak. A posterior leaf spring design has a thinner, flexible section near the ankle that acts like a spring, allowing some movement while still preventing the foot from dragging. The leaf spring version is more common for isolated foot drop because it allows a more natural stride.
Physical Therapy
Targeted exercises help maintain range of motion in the ankle and strengthen whatever muscle activity remains. Common exercises include towel stretches (looping a towel around the ball of your foot and pulling gently toward you to stretch the calf), ankle alphabet exercises (tracing letters in the air with your big toe to work the ankle through its full range), and single-leg balance work to retrain stability. As the nerve recovers, strengthening exercises progressively challenge the shin muscles to rebuild their ability to lift the foot.
Surgery
When foot drop is caused by a herniated disc compressing a nerve root, decompression surgery to remove the disc material can be highly effective. In one study of patients with foot drop from lumbar degenerative disease, 88% improved after surgery, with 61% making a complete recovery and another 27% showing meaningful improvement. No patients in that study got worse after surgery. Other studies report recovery rates between 61% and 84%. Surgery works best when the cause is direct physical compression of the nerve, not inflammation alone.
For fibular nerve compression at the knee, surgical release of the tissue trapping the nerve is sometimes performed when conservative measures fail.
Recovery: What to Realistically Expect
Recovery depends heavily on how severely the nerve was damaged. When the nerve is only partially injured (the signal is weakened but not completely blocked), about 65% of people eventually make a full recovery, with another 25% improving partially. When the nerve injury is complete, meaning no signal gets through at all, full recovery drops to around 40%, though roughly 55% still see some improvement.
The timeline is often longer than people expect. In a review of patients recovering from fibular nerve injuries, 62% didn’t reach their maximum recovery until more than 12 months after the injury. About 14% needed more than two years. Nerves regenerate slowly, and patience is essential. During this window, bracing and physical therapy protect the ankle joint, prevent the calf from tightening up, and keep you mobile.
If you’ve noticed foot drop developing over days to weeks alongside back pain or leg pain, that pattern points toward a spinal cause worth investigating promptly. If it appeared after prolonged pressure on the outer knee (a long surgery, a hospital stay, a cast), the nerve at the fibular head is the likely culprit, and removing the source of pressure is the critical first step.