Hip Pain Radiating to the Leg or Knee: Finding the Source

Hip Pain Radiating to the Leg or Knee: Finding the Source

Pain radiating from the hip to the leg or knee can come from the hip joint, the lower back, muscles and tendons or the circulation. Learn what the path of the pain suggests, how it is diagnosed and the red flags.

Pain that travels from the hip down the leg does not always start in the hip joint. The most common sources are problems inside the hip joint, a pinched nerve root in the lower back, strained muscles and tendons around the hip and irritation of the structures on the outer side of the hip. Whether the pain runs down the front, side or back of the thigh, whether it goes below the knee and whether numbness comes with it are the most useful clues. It also helps to know that hip joint pain can sometimes be felt only in the knee, which is a common reason the wrong area gets treated.

This article explains the possible causes of pain radiating from the left or right hip to the leg and knee, how the path of the pain hints at its source, why children and teenagers need particular attention, how the diagnosis is made and when you should seek help without delay.

What is referred pain, and why can hip pain be felt in the knee?

Referred pain is pain felt somewhere other than where the problem actually is. The hip joint shares nerve supply (branches of the femoral and obturator nerves) with the front and inner thigh and the inner side of the knee. The brain can interpret signals from the joint as if they were coming from those areas. As a result, hip arthritis or another hip joint problem may show up in some people as pain in the front of the thigh or around the kneecap rather than in the groin.

Likewise, the nerve roots that leave the lumbar spine supply specific parts of the leg. A compressed nerve root in the back can cause pain in the buttock and leg even though the problem lies in the spine. "Pain from the hip down the leg" is therefore a description shared by several different conditions.

Likely sources based on the path of the pain

From the groin down the front of the thigh to the knee

Pain that starts in the groin and runs down the front and inner thigh toward the knee, and is worse when walking, standing up or turning the leg inward, may come from the hip joint. Hip osteoarthritis, femoroacetabular impingement, labral tears and avascular necrosis belong in this group. This pain usually stops at the knee. With hip-related knee pain, the knee examination is often normal, while hip movement, particularly internal rotation, is limited and painful. We cover this in more detail in the differences between hip and knee pain.

From the side of the hip down the outer thigh

Pain that starts at the bony point on the outer hip and spreads down the side of the thigh is usually linked to the gluteal tendons and bursae. It typically worsens when lying on that side or climbing stairs. Burning, tingling and skin sensitivity on the outer thigh suggest compression of the nerve that supplies sensation to that area, known as meralgia paresthetica, which can be triggered by tight belts or trousers, excess weight and pregnancy.

From the buttock down the back of the leg and below the knee

Pain that starts in the buttock and runs down the back of the thigh past the knee to the calf or foot, with numbness or tingling, most often points to nerve root compression in the lower back (sciatica). Bending forward, coughing or sitting for long periods may make it worse. The piriformis, a deep buttock muscle, can also irritate the sciatic nerve and cause a similar picture, as explained in our article on piriformis syndrome and sciatica. Sacroiliac joint problems can cause pain in the buttock and back of the thigh, but it rarely goes below the knee.

Leg pain that comes on with walking and eases with rest

Pain in the buttock, thigh or calf that appears after walking a certain distance and settles within minutes of stopping may be due to narrowed leg arteries. It is more common in smokers and in people with diabetes or high cholesterol. Lumbar spinal stenosis can also cause leg pain on walking, but it typically eases when you bend forward or sit down. Both need assessment by the appropriate specialists.

Is left-sided pain different from right-sided pain?

For muscle, joint and nerve causes there is no meaningful difference between the two sides. A disc herniation usually bulges toward one side, so sciatica tends to affect one leg, and which leg depends on the direction of the herniation. Pain in both legs, or weakness and numbness on both sides, may point to a more widespread problem such as spinal stenosis and should not be ignored.

Why knee pain in children and teenagers deserves special attention

In children and adolescents, knee or thigh pain without a clear knee injury can come from the hip. Conditions such as a slipped capital femoral epiphysis or disrupted blood supply to the femoral head may first appear as knee pain and a slight limp. A child who limps and complains of knee pain should have their hip examined as well, because treatment options are broader when these conditions are recognised early.

How is the source found?

Your doctor will ask where the pain starts, the path it follows, which movements and positions make it worse and whether you have numbness or weakness. The examination typically includes:

• Hip range of motion, and whether flexion with internal rotation reproduces the pain
• Tenderness on the outer hip and strength of the hip abductors
• Back movement, the straight leg raise test, reflexes, sensation and muscle strength
• Examination of the knee itself for swelling, meniscus and ligament problems
• Leg pulses and circulation

Depending on the findings, a pelvic X-ray, an MRI of the hip or spine, nerve conduction studies or a vascular ultrasound may be requested. When it is unclear whether the pain comes from inside the joint, a diagnostic local anaesthetic injection into the hip can help: if thigh and knee pain clearly ease afterwards, the hip joint becomes the more likely source. The diagnosis is confirmed by interpreting the examination and test results together.

Treatment targets the source, not the spot

With referred pain, treatment is aimed at the source rather than where the pain is felt. Treating only the knee in hip-related knee pain rarely brings enough relief, whereas addressing the hip can also ease the knee. Muscle and tendon problems are usually managed with activity changes, physiotherapy and hip strengthening, and nerve root compression is generally treated first with medication, physiotherapy and exercise.

For impingement, labral tears or cartilage damage inside the hip that do not settle with non-surgical care, joint-preserving options such as hip arthroscopy may be considered in suitable patients. At Prof. Dr. Gökhan Polat's clinic, treatment is planned once the source is clear, taking into account age, activity level and personal goals, and response varies from person to person. See our hip joint diseases page for more information.

When should you see an orthopedic surgeon?

• Pain radiating from the hip down the leg that has not eased, or is worsening, after two to three weeks
• Pain that starts in the groin, runs to the knee, increases with walking and causes a limp
• Pain that wakes you at night
• Numbness, tingling or weakness, such as difficulty lifting the foot
• Knee pain that persists despite knee treatment when the knee examination is normal
• A child or teenager who limps and complains of knee or thigh pain

Seek urgent care if: you develop rapidly worsening leg weakness, loss of bladder or bowel control or numbness in the groin and genital area, which may indicate serious nerve compression. One-sided calf swelling, redness and tightness may signal a blood clot, and a suddenly cold, pale and very painful leg may mean a blocked artery. Hip pain with fever and an inability to move the joint should also be assessed the same day.

In summary

• Pain from the hip down the leg can come from the hip joint, the lower back, muscles and tendons or the circulation.
• Groin-to-knee pain points more toward the hip joint; pain below the knee with numbness points more toward a nerve root in the back.
• Hip problems can show up as knee pain alone, so the hip should always be examined, especially in children and teenagers.
• Treatment is planned around the source, not where the pain is felt.

This article is for general information only; diagnosis and treatment decisions are made individually after examination and the necessary tests.