Referred pain is any pain felt in a specific area originating in a different part of the body. The pain is not caused by any physical injury, trauma, or other issues in the area where it is actually felt.
For instance, problems in the lower back can cause pain in the knees, legs, and in severe cases, in the feet. This is because the nerves in the legs originate from the spinal cord. Irritation in any of these spinal nerves could result in knee pain.
Signs that your knee pain may be originating in your back
- Knee pain accompanied by back pain
- Nerve root affection is the likely cause of knee pain in the absence of trauma, injury, or underlying cause in the knee if it also accompanies back pain. The nerve roots that exit the second, third and fourth lumbar spine have nerve fibers that extend to the knees.
- When any of these nerve roots is impinged due to sciatica, disk herniation, or other condition, it can result in back and knee pain. Aside from pain, the individual may feel numbness and tingling sensations from the back down to the affected knee. The affected individual may also experience weakness of the thigh muscles and giving-out or buckling of the knee.
- Tightness of hamstring muscles
- The sciatic nerve passes through the gluteal region and innervates (supplies with nerves) the hamstring’s muscles. Irritation of the sciatic nerve could result in hamstring pain leading to tightness and weakness of the muscles.
- This pain will make it difficult to bend the knee, causing further hamstring tightness. A hamstring tightness that does not get better with stretching and accompanies persistent pain (or pain that resolves but returns later) may be due to a spinal problem that affects the nerve roots innervating the muscles of the legs.
- Bunion formation
- The sacrum is the part of the spine between the lumbar spine (lower back) and the coccyx (tail bone). The nerve roots that exit in the fifth lumbar spine and first sacral spine send nerve fibers to the muscles of the lower leg that stabilize and move the foot.
- When these nerves become severely irritated, it could affect the muscles that control the outside of the foot, causing overpronation of the foot, otherwise known as flat foot. Foot pronation causes the tip of the big toe to tilt inwards towards the second toe and the base of the big toe to move outwards, forming a bunion.
Referred pain typically resolves once the problem that is causing the back pain is solved. Therefore, diagnosing the condition causing the back pain and referred pain is vital to determine the appropriate treatment.
Physicians usually employ conservative management for back pain with referred pain in the legs. This includes rest to give time for healing and for the inflammation (if any) to subside, pain medications, and physical therapy intervention.
Physical therapy interventions include exercises for the back to help decompress the spine and release the impinged nerve. Interventions also include stretching and strengthening exercises to improve flexibility and strength of the lower back muscles, hamstrings and other thigh muscles, and muscles of the lower leg and foot.
Your physical therapist may also employ functional training to control the weakened muscles and allow a return to daily activities. The physical therapist will also teach proper posture and proper body mechanics to prevent the injury from occurring again.
If the conservative treatment is not successful, additional evaluation procedures such as discogram or discography – an imaging technique that assesses back pain – could be done to examine the problem further and determine its cause.
Surgery is the last option given to patients with severe and long-standing back pain. This is because the surgery involves many risks that can result in other potential problems, such as damage to the spinal cord, bacterial infection and poor healing.
How does the spine cause knee pain?
Lower back pain ranges from mild pain due to muscle strain to a more severe type of pain that radiates to the lower leg and feet. Several conditions cause back pain that radiates down the knees. Some of these conditions are:
- The five nerve roots of the bones in the lower back – the lumbar spine – join together as they exit the spine to form the sciatic nerve. The sciatic nerve is the longest and largest nerve in the body. It runs deep through the buttocks, to the back of the thigh and knee, and down to the ankle and foot. The sciatic nerve links the spinal cord with the skin and muscles of the entire lower leg and foot.
- If the sciatic nerve becomes inflamed, irritated, or compressed in the lumbar spine, it can cause an array of symptoms, including lower back pain and referred pain in the legs and the knees. This condition is called sciatica.
- Sciatica often causes sharp, shooting, stabbing pain and tingling sensations in the lower back, buttocks, back of the thighs, knees, and sometimes the feet. Typically, only one side of the body experiences these sensations.
- Lumbar Herniated Disk
- The vertebrae (bones of the spine) are separated and cushioned by a rubbery pad called the spinal disk or intervertebral disk. These disks support the spine and absorb shock during movements.
- When there is too much pressure in the spine, the intervertebral disk’s outer covering (annulus) may tear. This tear could lead to the inner disk tissue bulging out. The protruded tissue may push and compress the spinal nerve root near it, causing referred pain. Almost all disk herniation occurs in the lumbar spine, which results in extreme pain in the lower back. If the nerve root is affected, the pain may radiate to the thighs, knees and feet. This pain usually occurs on only one side of the body.
- Spondylolisthesis is a condition where a vertebra becomes unstable and glides out of its position. The slipped vertebra could pressure or compress the nerve root, leading to pain in the lower legs, including the knees.
- Most cases of spondylolisthesis do not have symptoms. The referred pain in the leg and knee is a result of nerve roots pinching due to the sliding of vertebrae.
- Lumbar Spinal Stenosis
- A tunnel called the spinal canal is found between two vertebrae. This canal is where the nerve roots from the spinal cord exit and serve the lower parts of the body. Lumbar spinal stenosis is when the spinal canal in the lumbar spine becomes narrow, causing pressure on the spinal cord or the nerve root that exits it.
- The condition called lumbar spinal stenosis results in lower back pain and numbness at the back of the leg. In severe spinal stenosis, controlling the bladder and bowel functions may become difficult.
Dr Aarti is an MBBS (Bachelor of Medicine and Surgery) from Baroda Medical College (The Maharaja Sayajirao University, Baroda). Dr. Aarti has also completed her Masters of Medical Science and Technology from the prestigious Indian Institute of Technology, Kharagpur.