Knee pain is a common complaint that affects people of all ages. The causes of knee pain range from injury to arthritis and other degenerative conditions. Sometimes, knee pain can originate from a problem in the back, specifically the L5-S1 segment of the spine.
What is L5-S1?
The L5 and S1 vertebrae are located at the bottom of the lumbar spine, right above the sacrum. The L5-S1 segment is where the L5 vertebra connects with the S1 vertebra.
This segment allows movement between the lumbar spine and pelvis. It bears a significant amount of weight and stress as it supports the upper body.
L5-S1 is also the segment where many nerve roots exit the spine. The L5 nerve root exits between the L5 and S1 vertebrae, while the S1 nerve root exits just below S1. These nerve roots come together to form the sciatic nerve, which runs down the back of each leg.
How L5-S1 problems can cause knee pain
Issues with the L5-S1 segment can irritate the nerve roots exiting here, causing pain, numbness or weakness that radiates down the leg. This is commonly referred to as sciatica or radiculopathy.
The L5 nerve root specifically connects with and provides sensation to the shin and top of the foot. The S1 nerve root connects with the outer part of the foot and ankle. Irritation of these nerves can cause symptoms that radiate down the back of the leg, into the knee.
Some common L5-S1 problems that can contribute to knee pain include:
- Degenerative disc disease – Breakdown of the cushioning discs between vertebrae
- Disc herniation – Bulging or rupture of a disc pressing on the spinal nerves
- Spinal stenosis – Narrowing of the spinal canal putting pressure on the nerves
- Spondylolisthesis – Vertebral slippage causing nerve compression
- Arthritis – Facet joint arthritis can cause inflammation affecting nearby nerves
The sciatic nerve also provides some innervation to the knee joint itself. Irritation of this nerve can cause pain to radiate into the knee.
Symptoms of L5-S1 issues causing knee pain
Knee pain originating from an L5-S1 problem typically has the following characteristics:
- Pain radiating from the buttock/hip down the back of the thigh into the knee
- Numbness or tingling into the shin, ankle, foot and/or knee
- Pain when bending, extending or bearing weight on the knee
- Weakness in the knee, ankle or foot
- Foot drop – Dragging of the foot when walking due to weakness
- Low back pain may be present
The knee pain is usually one-sided, affecting only the involved leg. The exact location and severity of symptoms can vary depending on the distribution of nerve irritation.
How is an L5-S1 issue diagnosed as the cause?
If an L5-S1 issue is suspected to be causing knee pain, a physician will perform a thorough medical evaluation. This includes:
- Medical history – Discuss symptoms, daily activities, past injuries
- Physical exam – Assess range of motion, stiffness, areas of pain/numbness
- Neurological exam – Test reflexes, muscle strength, and sensation
- Imaging – X-ray, MRI to view the spine and detect sources of compression
- Electrodiagnostic tests – EMG/nerve conduction studies check for nerve dysfunction
These tests can help confirm that knee pain is coming from an L5-S1 nerve root problem rather than an issue with the knee joint itself.
How is L5-S1 knee pain treated?
Treatment focuses on both relieving nerve root irritation and reducing low back pain. Options may include:
- Medications – Oral steroids, NSAIDs, muscle relaxers or neuropathic pain medications
- Epidural steroid injection – Steroids injected near irritated nerve roots to reduce inflammation
- Physical therapy – Stretching, strengthening exercises and modalities to improve mobility and support
- Spinal decompression – Techniques like traction to take pressure off compressed nerves
- Surgery – When conservative treatment fails, surgery may be considered to remove pressure on nerves
The goal is to resolve nerve irritation to eliminate radiating symptoms. Treatment also focuses on strengthening and stabilizing the spine to prevent recurrence.
What is the prognosis for L5-S1 knee pain?
The prognosis depends on the specific cause and response to treatment. Mild issues like a strained muscle often resolve in a few weeks with conservative care. More advanced degenerative problems sometimes require surgery or longer-term management.
With appropriate treatment, many patients see significant improvement or complete relief of their knee pain stemming from L5-S1. However, some cases can be chronic and difficult to resolve.
Regular follow-up with a spine specialist is important to monitor symptoms and adjust treatment if needed. Physical therapy and home exercise help maintain mobility and prevent future flare-ups.
Key Points
- Irritation to the L5 and S1 nerve roots can cause pain and numbness to radiate down the leg into the knee.
- Common L5-S1 problems like degenerative disc disease, spinal stenosis and spondylolisthesis can contribute to this type of knee pain.
- Diagnosis involves a medical history, physical exam, imaging tests and electrodiagnostics to pinpoint the source.
- Treatment aims to resolve nerve inflammation and may include medications, injections, therapy, decompression or surgery.
- With proper management, most patients find improvement or resolution of knee pain stemming from L5-S1.
The Bottom Line
Knee pain can sometimes originate from a problem in the lumbar spine, specifically the L5-S1 segment. Issues here can cause inflammation or compression of the associated nerve roots, leading to radiating pain, numbness or weakness down the leg to the knee. Diagnosing the L5-S1 segment as the source of knee pain involves a comprehensive medical workup. Treatment focuses on relieving nerve irritation as well as stabilizing the low back. With the right management plan, resolution of L5-S1-related knee pain is often achievable.
Frequently Asked Questions
Can a herniated disc at L5-S1 cause knee pain?
Yes, an L5-S1 herniated disc is a common cause of radiating knee pain. A herniated disc irritates or compresses the nearby nerve roots, which can send pain signals down to the knee.
Does S1 radiculopathy cause knee pain?
S1 radiculopathy, or irritation/compression of the S1 nerve root, frequently causes pain to radiate down the back of the leg into the knee. Numbness and weakness in the foot/ankle may also occur.
Can spinal stenosis in the lower back cause knee pain?
Yes, spinal stenosis in the lower back can contribute to knee pain. When the spinal canal narrows it can compress the nerve roots, including those at L5-S1, leading to radiating symptoms down the leg.
What are the most common causes of L5-S1 problems?
The most common causes are degenerative changes like disc degeneration, facet arthritis, ligamentum flavum hypertrophy contributing to spinal stenosis, and spondylolisthesis. Injuries, tears, or herniation of the discs between L5-S1 also frequently occur.
Is knee pain always caused by an L5-S1 issue?
No, there are many other potential causes of knee pain including knee joint, tendon or ligament injuries, arthritis, overuse, and inflammatory conditions. A full medical workup helps determine whether L5-S1 issues are contributing to knee pain symptoms.
References
- Bajwa SJ, Hald A. Lumbar transverse process fractures presenting with acute lumbar radicular pain. J Emerg Med. 2012;43(5):686-690. doi:10.1016/j.jemermed.2012.01.035
- Koes BW, van Tulder M, Peul WC. Diagnosis and treatment of sciatica. BMJ. 2007;334(7607):1313-1317. doi:10.1136/bmj.39223.428495.BE
- Kreiner DS, Hwang SW, Easa JE, et al. An evidence-based clinical guideline for the diagnosis and treatment of lumbar disc herniation with radiculopathy. Spine J. 2014;14(1):180-191. doi:10.1016/j.spinee.2013.08.003
- Osterman M, Ilyas AM, Matz PG. Minimally Invasive Spine Surgery for Degenerative Conditions of the Lumbar Spine. Orthop Clin North Am. 2016;47(4):535-543. doi:10.1016/j.ocl.2016.06.005
- Vroomen PC, de Krom MC, Wilmink JT, Kester AD, Knottnerus JA. Diagnostic value of history and physical examination in patients suspected of lumbosacral nerve root compression. J Neurol Neurosurg Psychiatry. 2002;72(5):630-634. doi:10.1136/jnnp.72.5.630