Tennis elbow typically produces tenderness close to the common extensor tendon origin on the outside of the elbow, with pain on gripping or resisted wrist extension. Radial tunnel syndrome, a compression problem of the posterior interosseous branch of the radial nerve, tends to produce pain in the upper forearm and can feel very similar. The two can resemble each other and can coexist. No single test separates them reliably, which is why persistent lateral elbow pain should not automatically be treated as tendon disease.
Why this distinction matters
Most lateral elbow pain is tendon-related. But if a nerve is contributing, treatment aimed only at the tendon may not address the whole problem. Two 2026 studies of people diagnosed with tennis elbow suggest this is not rare, especially in cases that have not responded to treatment. The goal is not to find a nerve problem in everyone. It is to avoid assuming there is never one.
What is tennis elbow?
Tennis elbow, or lateral elbow tendinopathy, involves the common extensor tendon where the wrist and finger extensor muscles attach to the outside of the elbow, often including the extensor carpi radialis brevis (ECRB). Chronic cases show degenerative tendon change rather than ongoing inflammation. The 2022 clinical practice guideline on lateral elbow pain describes symptoms as driven by an interaction of tendon changes, motor control changes and pain processing.
Typical features:
- Pain and tenderness close to the bony point on the outside of the elbow (the lateral epicondyle)
- Pain with gripping, lifting with the palm down, or resisted wrist extension
- Reduced grip strength because of pain
- No numbness or tingling
What is radial tunnel syndrome?
The radial nerve divides near the elbow. Its deep motor branch, the posterior interosseous nerve, passes through a tunnel of muscle and fascia in the upper forearm, including under the edge of the supinator muscle. Intermittent compression along this path is called radial tunnel syndrome.
Reviews describe it as lateral elbow and upper-forearm pain that may spread toward the wrist, without obvious muscle weakness. When weakness of finger or thumb extension is present, the condition is usually called posterior interosseous nerve syndrome instead. Radial tunnel syndrome remains debated. A 2023 review in the Journal of the American Academy of Orthopaedic Surgeons noted ongoing controversy about how to diagnose it with imaging and how best to treat it.
How do they differ?
| Feature | Tennis elbow | Radial tunnel syndrome |
|---|---|---|
| Tissue | Common extensor tendon origin | Posterior interosseous nerve |
| Where it hurts most | At or just below the lateral epicondyle | Usually farther down, over the upper forearm muscles |
| Common provocation | Gripping, resisted wrist extension | Resisted middle-finger extension, resisted supination, pressure over the nerve's path |
| Numbness or tingling | Not expected | Usually absent, since the nerve branch is mainly motor |
| Nerve conduction tests | Normal | Often normal |
These are tendencies, not rules. Resisted middle-finger extension, for example, loads the ECRB and can hurt in tennis elbow as well. A tender point in the forearm does not by itself make the problem neural.
Can they coexist?
Yes, and recent research suggests it is not unusual in stubborn cases.
Ultrasound-guided nerve blocks. Keles and colleagues, in the American Journal of Physical Medicine and Rehabilitation in 2026, studied 32 people whose tennis elbow had lasted at least six months despite treatment. They used an ultrasound-guided block of the posterior interosseous nerve as the reference test. By that standard, 44% met criteria for radial tunnel syndrome. Nerve conduction studies were normal in every patient, and the tendon's ultrasound appearance did not differ between those with and without the nerve component.
Electrodiagnostic testing. Çilingiroğlu and colleagues, in Acta Neurologica Belgica in 2026, tested 62 people with tennis elbow and 54 healthy controls. Electrophysiological signs of posterior interosseous nerve involvement appeared in 19.4% of patients and 1.9% of controls. Patients with and without those findings did not differ on provocative tests, range of motion, grip strength, pain or tennis elbow function scores.
The two studies used different definitions and reference tests, which is part of why their numbers differ. Both are small. Together they show that a nerve component can sit alongside tendon pain, and that it may not be visible on routine examination, standard ultrasound or nerve conduction testing.
Why one test cannot settle it
- Electrodiagnostic tests are often normal in radial tunnel syndrome, because the compression is intermittent and the symptoms are mainly pain.
- Imaging is inconsistent. In the 2026 nerve-block study, comparing nerve size with the other arm agreed only slightly with the diagnosis.
- Clinical tests overlap. A 2015 review emphasized that the clinical examination, especially the exact site of pain, matters more than tests. But pain-provocation tests for tendon and nerve load overlapping structures.
- Diagnostic nerve blocks can help, but they are an injection procedure done in a medical setting, not a routine screening test.
The practical answer is to build the picture from several findings rather than one.
What a careful examination looks at
- Exactly where the pain is, and whether it is on the bony point or farther down the forearm
- Which movements reproduce it: gripping, wrist extension, finger extension, forearm rotation
- Tenderness at the tendon origin compared with tenderness along the nerve's path
- Strength of wrist, finger and thumb extension
- Any numbness, tingling or symptoms spreading from the neck
- Elbow motion and any catching or locking, which point toward the joint
- How the pain has responded to tendon-focused care so far
Other causes of lateral elbow pain
- Radiocapitellar joint problems: catching, locking, clicking or loss of motion
- Cervical referral: neck pain with arm symptoms, numbness or weakness
- Tendon tear: a sudden injury, a pop or marked weakness
- Posterior interosseous nerve palsy: true weakness of finger or thumb extension needs prompt medical evaluation
What this means for treatment
If the examination points mainly to the tendon, treatment focuses on the tendon, typically starting with loading and strengthening. Options such as shockwave can be considered when pain persists. The evidence for those options is reviewed in shockwave therapy for tennis elbow.
If the findings suggest a nerve component, the plan changes. That may mean avoiding treatment directly over an irritated nerve, modifying activity, referral for nerve-focused testing, or physician evaluation. Reviews describe conservative care for radial tunnel syndrome as having limited lasting success, with surgical decompression considered when symptoms persist. If both are present, both need to be accounted for.
Persistent tendon problems elsewhere in the body follow the same logic, covered in chronic tendinopathy.
How Novo approaches lateral elbow pain
We examine first. The aim is to identify which tissue is driving the pain before choosing treatment, and to refer when the findings point outside what we treat. See how we approach tennis and golfer's elbow, or book a new patient exam.
References
- Keles A, Palamar D, Gunduz A, Akarirmak U. Ultrasonographic and electrophysiologic assessment of radial tunnel syndrome in patients with treatment-resistant lateral epicondylitis: insights into diagnostic utility and clinical implications. American Journal of Physical Medicine and Rehabilitation. 2026;105(4):330-337. PMID 41082715. (link)
- Çilingiroğlu Ç, Bilgilisoy Filiz M, Koldaş Doğan Ş, et al. Frequency of posterior interosseous nerve syndrome and its impact on clinical outcomes in patients with lateral epicondylitis: a prospective, controlled, electrophysiological study. Acta Neurologica Belgica. 2026;126(1):131-138. PMID 40853587. (link)
- Wolf JM, Patel R, Ghosh K. Radial tunnel syndrome: review and best evidence. Journal of the American Academy of Orthopaedic Surgeons. 2023;31(15):813-819. PMID 37276490. (link)
- Levina Y, Dantuluri PK. Radial tunnel syndrome. Current Reviews in Musculoskeletal Medicine. 2021;14(3):205-213. PMID 33890229. (link)
- Moradi A, Ebrahimzadeh MH, Jupiter JB. Radial tunnel syndrome, diagnostic and treatment dilemma. Archives of Bone and Joint Surgery. 2015;3(3):156-162. PMID 26213698. (link)
- Lucado AM, Day JM, Vincent JI, et al. Lateral elbow pain and muscle function impairments: clinical practice guidelines. Journal of Orthopaedic and Sports Physical Therapy. 2022;52(12):CPG1-CPG111. PMID 36453071. (link)
