Key Point

• Massage and soft-tissue therapy play particularly beneficial roles in treating radial tunnel syndrome. It is essential to address the entire arm comprehensively, so massage treatment should focus on the upper extremity and cervical regions.

Radial tunnel syndrome (RTS) is a perplexing and often misunderstood condition. Because it is not common, it can go unrecognized. Unfortunately, attempts at treating it can worsen the condition if that treatment is not specific to RTS. Like many conditions, this is one in which a greater understanding will improve your clinical decisions and provide your clients with better education and care. 

RTS can challenge even the most experienced massage therapists. It is frequently mistaken for other conditions, especially lateral epicondylitis (LE), commonly known as tennis elbow. This mistaken identity is why the cornerstone to effective treatment begins with your assessment. Distinguishing this painful condition with symptoms that mimic others is a prerequisite to getting these clients out of pain and back into activities. Let’s take an in-depth exploration of RTS. 

Anatomical Overview 

RTS is a nerve compression pathology affecting the radial nerve in the forearm. The radial nerve is one of three main nerve branches that run the entire length of the upper extremities. Compression pathologies of the radial nerve are less common because the radial nerve’s path has fewer vulnerable compression locations. However, the nerve is susceptible in the lateral elbow region, where RTS occurs. 

The other two nerve branches are the ulnar and median nerve branches and have more common pathologies. For example, the median nerve is affected by carpal tunnel syndrome. There are also numerous locations along the median nerve where compression can occur. Ulnar nerve compression is also common, with cubital tunnel syndrome (elbow) and Guyon’s canal syndrome (wrist) being the most prevalent.

The radial and other upper extremity nerves are part of the brachial plexus. After diverging from the brachial plexus, the radial nerve courses around the posterior aspect of the upper arm near the spiral groove of the humerus. It then crosses the anterior aspect of the elbow before continuing down the forearm. Just distal to the elbow, the radial nerve divides into the superficial and deep branches. The superficial branch is primarily sensory. The deep branch becomes the posterior interosseous nerve (PIN), mainly carrying motor fibers. Compression of the PIN is the primary problem in RTS. 

The supinator muscle also plays a critical role in this condition. The supinator has two divisions. One comes off the humerus’ lateral epicondyle, and some of its fibers also originate from the radial collateral and annular ligaments. The other division originates from the supinator crest and the fossa of the ulna (Image 1). 

The radial tunnel is a narrow passage in the elbow region and extends from the radial head to the inferior border of the supinator muscle. In the radial tunnel, the PIN passes between the two divisions of the supinator muscle. RTS is the compression of the PIN within the tunnel. A region along the superior border of the supinator, called the arcade of Frohse, is the most common region for PIN compression in RTS (Image 2). 

Exploring the Pathology

Several factors can cause radial nerve compression in the tunnel. Trauma to the elbow can displace bones in the elbow region, with the bone ends causing incursion into the radial tunnel and compressing the PIN. Small cysts or tumors can also compress the nerve in the tunnel. Tendinous bands in the supinator muscle that compress the nerve are the most common cause of RTS. 

RTS symptoms develop either suddenly or gradually, depending on the primary cause of the nerve compression. For example, RTS will often occur due to an acute injury. Acute injuries can cause a change in the positional alignment of the bones in the elbow. In this case, symptoms have a rapid onset in the traumatized area. In other cases, the symptoms are gradual, such as in cases of tumors or tendinous bands in the supinator muscle. Common nerve compression symptoms include paresthesia (pins and needles), sharp pain, and numbness. These symptoms are also common in the carpal tunnel or cubital tunnel syndromes. They result from pressure on many sensory fiber trunks within the nerve. An important distinction is where the pain and sensory symptoms are felt. That is why it is helpful to become familiar with the regions of cutaneous innervation of the distal forearm. 

Because the PIN is primarily a motor nerve, the usual symptoms of paresthesia and sharp pain are uncommon. Instead, clients with RTS usually describe dull, nonspecific, aching pain in the forearm. That pain results from irritation of the few sensory fibers within the PIN. Pain tends to increase with forearm supination and pronation movements. These movements are usually more painful if performed with elbow extension. The elbow extension further stretches the nerve against adjacent structures. 

Assessment

Gathering information and the history of the symptom onset and pain patterns is essential. Revisit the patterns and symptoms described above. You might see weakness in the wrist and finger extensors that are innervated by motor fibers in the PIN. Motor or sensory symptoms may exist together or without the presence of the other. Be sure to ask about repetitive motion activities affecting the forearm, such as handwriting, which can be an issue because of extensive isometric forearm muscle contractions. 

RTS presents with dull, aching forearm pain, which will show up with palpation directly over the radial tunnel. Those symptoms may increase with forearm pronation, which stretches the supinator. As this muscle stretches, it pulls taut against the adjacent nerve. Resisted forearm supination can also increase symptoms. Muscle weakness is another common finding and can be found in the wrist and finger extensors. 

Nerve conditions are known to be challenging to identify, which is also true for RTS. This condition shares symptoms with other conditions, such as tennis elbow. In this case, the symptoms are so similar that RTS is often called “resistant tennis elbow.” If you suspect LE and the symptoms get worse with treatment or don’t resolve, you should consider the possibility of RTS.

The key to distinguishing between these conditions is assessment that evaluates the pain location and differences in movement. LE is a chronic overuse condition affecting the wrist extensor tendons at their proximal attachment (the lateral epicondyle). The elbow pain of LE is most pronounced right at the epicondyle, so palpate the attachment site of the common extensor tendons to investigate this condition. In RTS, you are more likely to find dull, aching pain in a broad area of the forearm extensor muscle bellies, so palpate by pressing on the forearm extensor muscles (back side of the forearm), not near the elbow. 

The upper limb neurodynamic tests (ULNT) are nerve evaluation tests; there are four—No. 1 and No. 2 test the median nerve, No. 3 the radial, and No. 4 the ulnar nerve (see the video of the No. 3 test by scanning the QR code on page 27). ULNT No. 3 can help distinguish epicondylitis from RTS by increasing the pulling (tensile) force on the upper extremity nerves, which usually heightens symptoms. This test is a series of movements that gradually increase tension on the radial nerve. A positive result occurs if symptoms increase during any of the movements as each movement further stretches the radial nerve. Remember that wrist flexion (performed in the ULNT No. 3 test) also stretches the tendons involved in LE. 

The client’s movement should also be evaluated. Palpating the attachment site during resisted wrist extension usually increases LE pain significantly. Weakness without significant pain during resisted wrist extension is more likely in RTS. Also, note if pain increases with lateral neck flexion to the opposite side. Lateral neck flexion stretches the radial nerve but not the wrist extensor tendons. Increased pain with that movement is more indicative of nerve involvement. 

Treatment

Conservative measures, such as rest and activity modification, should form the cornerstone of care for RTS. Absolute rest is unnecessary, but many RTS cases will resolve independently by reducing offending activities. In some cases, bracing or splints are used to reduce forces on the affected tissues, giving the nerve time to heal. In some cases, anti-inflammatory drugs (NSAIDs) are prescribed to reduce inflammatory activity affecting the PIN. These drugs don’t have a high degree of effectiveness on their own and are best as adjuncts to other treatments. 

Massage and soft-tissue therapy play particularly beneficial roles in treating RTS. It is essential to address the entire arm comprehensively, so the massage treatment should focus on the upper extremity and cervical regions. Treating the radial nerve’s entire path can improve its mobility. A variety of massage techniques help address RTS. The primary goal is to reduce local muscle tightness. Pay particular attention to the wrist and finger flexor muscles because the bellies of these muscles have sensory fibers going back to the PIN that often produce the most pain. 

Remember that symptoms in the forearm can involve neural pathology in other parts of the upper extremity. When there is more than one site of compression on a nerve, it is called the double or multiple crush phenomenon. For instance, there could be radial nerve compression in the thoracic outlet. Compression in this region would further aggravate forearm symptoms. In that case, the thoracic outlet region should be addressed as part of the comprehensive treatment. The axillary area is another region where the radial nerve is vulnerable, particularly for people putting excess pressure in this region. An example would be someone walking on crutches, in which the upper brace of the crutch presses up into the axilla and compresses the radial nerve.

Treatments generally begin with superficial applications to settle the nervous system and begin to relax the tissues. After this, deeper methods aimed at reducing hypertonicity can be applied. Stripping techniques should start with a broad contact surface like the palm or fist. By spreading pressure across the different muscles, the application decreases sensitivity and does not overtax any muscle.

After the broad contact applications, small contact surface methods are effective. This means the pressure is concentrated over a smaller area, allowing for more precisely targeted treatment. Longitudinal stripping will work these muscles very thoroughly. Pay attention to increased neural sensitivity or increased pain for the client. That could indicate adverse pressure on the affected nerves. 

After passive longitudinal stripping methods, active stripping methods are helpful. Active stripping methods involve the longitudinal stroke and eccentric wrist flexion (Image 3). This same concept can be employed with the supinator muscle. Perform a short stripping motion on the supinator during eccentric forearm pronation. 

Active techniques are very effective, but why they work has yet to be solved. Muscle action, along with the massage application, may help normalize neurological activity, which is important in reducing pain. Deep, specific, active work can also encourage greater neural mobility. One of the issues that leads to neural irritation is improper mobility.

There are a couple of cautions to be aware of when treating RTS. Because RTS is a nerve condition, communication with the client is paramount, and paying attention to how the client responds to the treatment is critical. Ensure your client knows they should alert you to increased neural symptoms as you work. Although deep friction massage is commonly used to treat the lateral epicondyle, excessive friction in this area could further irritate PIN compression. Additionally, pay attention to the amount of pressure used and note any changes in the client’s pain and comfort with deep stripping along the neural pathway. 

Finally, physical therapy, especially exercises focusing on stretching and strengthening the forearm muscles, can be an effective treatment. Forearm conditioning can reduce the impact on the adjacent nerve. If these traditional treatments are not successful, surgery may be the next choice. Surgical procedures focus on releasing any structures compressing the nerve. 

Conclusion

RTS is not a commonly occurring condition. However, it can be painful and debilitating if it’s not recognized or is confused with another condition. Its symptoms are often mistaken for LE, which is prevalent. Consequently, clinicians may prematurely conclude that LE rather than RTS is the primary problem. This misjudgment could lead to inappropriate treatment that aggravates the existing complaint.