When Knee Pain Was Actually a Spine Problem
A patient advised to undergo total knee replacement at another centre — until the right team asked the right question.
A middle-aged patient in Mumbai presented with persistent anterior knee pain. Knee X-rays and examination were normal. He was advised total knee replacement at another centre. At Alpha Ortho, a combined spine and knee evaluation identified quadriceps weakness, a reduced patellar reflex, and a pain distribution inconsistent with a knee cause. MRI lumbar spine showed an L3-L4 foraminal disc extrusion compressing the L3 nerve root (L3 radiculopathy). A targeted L3 nerve root block injection produced significant symptom relief, and the patient avoided knee replacement surgery.
Presenting Complaint
True Diagnosis
Treatment Received
The Patient's Journey Before Alpha Ortho
A middle-aged patient presented with a long history of persistent anterior knee pain — pain in the front of the knee and inner thigh. There was no trauma, no injury, and knee X-rays were entirely normal.
He had been managed conservatively at multiple centres, with the diagnosis consistently pointing to the knee. When conservative treatment failed, the patient was advised to undergo a total knee replacement at another hospital in Mumbai.
Seeking a second opinion, the patient was referred to our orthopaedic knee specialist at Alpha Ortho, Kandivali West, Mumbai.
What the Knee Examination Revealed
A careful clinical evaluation produced a picture that did not fit primary knee pathology. Several neurological signs pointed to a different source entirely.
Findings on Examination
The pain radiation pattern (anterior thigh to medial knee), reduced patellar reflex, and quadriceps weakness together pointed to the L3 nerve root rather than the knee joint. The patient was referred to spine surgeon Dr. Yogin Patel for further evaluation.
MRI Reveals the Real Culprit
MRI of the lumbar spine was requested. The findings were unambiguous and explained every symptom the patient had attributed to his knee.
MRI LS Spine finding: L3-L4 foraminal disc extrusion with significant compression of the L3 nerve root — consistent with L3 radiculopathy.
The L3 nerve root carries sensory fibres from the anterior thigh and medial knee. When compressed by the extruded disc at L3-L4, the brain interprets this as knee and thigh pain — a well-recognised phenomenon of referred radicular pain. The knee itself was entirely normal throughout.
A Targeted Injection Instead of Major Surgery
With confirmed L3 radiculopathy, the management plan changed completely. Rather than knee replacement, the patient received a targeted L3 nerve root block — a minimally invasive, image-guided injection.
Knee Pain
Months of conservative Rx
Alpha Ortho
Knee + Spine joint eval
MRI Spine
L3-L4 disc extrusion
L3 Nerve Root Block
Significant relief
Knee Replacement
Unnecessary major surgery
The outcome: significant relief of knee and thigh pain following a single targeted injection. An unnecessary total knee replacement — with its operative risks, prolonged recovery, and cost — was avoided entirely.
“Not every knee pain is a knee problem. The right diagnosis is the most important operation we perform.”
— Dr. Yogin Patel, Spine Surgeon, Alpha Ortho, Kandivali, Mumbai
Key Learning Points
The L3 nerve root supplies the anterior thigh and medial knee. Disc compression at L3-L4 causes pain in these areas — not always a knee joint problem.
SLR tests L4-S1 roots only. Upper lumbar radiculopathy (L2, L3) gives a consistently negative SLR, providing false reassurance.
Quadriceps weakness and a reduced patellar reflex are the key neurological signs for L3 involvement and must not be missed.
A gait abnormality unexplained by local joint disease should trigger neurological evaluation of the lumbar spine.
When knee investigations are unremarkable and symptoms persist despite treatment, the lumbar spine must be included in the workup.
This outcome was possible because a knee surgeon and spine surgeon worked as an integrated team within Alpha Ortho.
Why This Presentation Is Easy to Miss
Upper lumbar radiculopathy — L1, L2, and L3 roots — is significantly less common than lower lumbar disc disease and less familiar to most clinicians. Unlike the classic sciatica of L4-S1 involvement (posterior thigh, calf, foot), L3 radiculopathy produces pain in the anterior thigh and medial knee: regions associated in the clinical mind with the knee joint itself.
A critical clinical pearl: the Straight Leg Raise (SLR) test is an unreliable screen for upper lumbar radiculopathy. It evaluates primarily the L4, L5, and S1 roots and will typically be negative in L2 or L3 involvement. This creates dangerous false reassurance — the examining clinician passes the “spine screen” and returns focus to the knee.
The appropriate bedside tests for L3 root involvement are the femoral nerve stretch test (prone knee flexion), careful grading of quadriceps power (L3/L4 myotome), and assessment of the patellar reflex (L3/L4 reflex arc). Together, these three signs reliably differentiate a spinal source from a primary knee diagnosis.
Questions Patients & Clinicians Ask
These questions are answered for educational purposes. If you have persistent knee or thigh pain that has not responded to treatment, consult a qualified orthopaedic or spine specialist.
Can spine problems cause knee pain?+
Yes. The L3 nerve root in the lumbar spine supplies sensation to the anterior thigh and medial knee. When a disc at the L3-L4 level compresses this nerve root, patients experience pain in the front of the thigh and inner knee — which is commonly mistaken for a knee joint problem. This is called L3 radiculopathy.
What is L3 radiculopathy?+
L3 radiculopathy is compression or irritation of the L3 nerve root in the lumbar spine, usually caused by a disc herniation or foraminal narrowing at the L3-L4 level. It causes pain in the anterior thigh and medial knee, weakness of the quadriceps muscle, and a reduced patellar (knee jerk) reflex.
Why does L3 radiculopathy feel like knee pain?+
The L3 nerve root carries sensory fibres from the anterior thigh and medial knee to the brain. When this nerve is compressed in the spine, the brain interprets the signal as pain originating in the knee — a phenomenon called referred pain or radicular pain. The knee itself is entirely normal.
Can a straight leg raise (SLR) test detect L3 radiculopathy?+
No. The straight leg raise test primarily stresses the L4, L5, and S1 nerve roots. It is frequently negative in upper lumbar radiculopathy involving L2 or L3 roots. A normal SLR does not rule out a spinal cause of knee or thigh pain. The femoral nerve stretch test is more appropriate for detecting L3 involvement.
How is L3 radiculopathy treated?+
Treatment options include conservative management (physiotherapy, NSAIDs), targeted L3 nerve root block injections for pain relief, and surgery (such as microdiscectomy or endoscopic decompression) in refractory cases. In this case, a single nerve root block produced significant relief.
What are the signs that knee pain is coming from the spine?+
Warning signs include: normal knee X-rays and MRI; pain that radiates from the thigh to the knee rather than starting at the knee; weakness of the quadriceps; a reduced or absent patellar reflex; abnormal gait suggesting a neurological cause; and failure to improve with knee-directed treatment.
Where can I see a spine surgeon in Kandivali Mumbai?+
Dr. Yogin Patel is a spine surgeon at Alpha Ortho, Kandivali West, Mumbai. He specialises in minimally invasive spine surgery and manages conditions including disc herniations, radiculopathy, spinal deformity, and spinal infections. Alpha Ortho is a multi-surgeon orthopaedic and spine clinic serving Kandivali, Borivali, Malad, and surrounding areas.