Introduction

Being able to eat and speak normally is a privilege we often take for granted. For those affected by trismus, simple and easy tasks are a major struggle. So, what exactly is trismus? Trismus is a condition in which the jaw muscles tighten so severely that it makes it painful and difficult to open the mouth. This condition comes from muscle spasms that surround the jaw joints, also known as the temporomandibular joints (TMJ). Trismus can arise from a wide range of causes, including dental procedures, jaw injuries, infections, TMJ disorders, and certain neurological or inflammatory conditions. It is also a well-recognised side effect of treatment for head and neck cancer, particularly radiation therapy.

Physical therapy plays a crucial role in managing trismus by reducing pain and restoring jaw mobility. This article reviews trismus and explores how various physical therapy techniques, including heat therapy and jaw stretching, can be utilised to manage trismus. This article will also highlight the importance of physical therapy and how it can improve the overall quality of life for individuals affected by this condition.  

Understanding trismus

Definition and clinical presentation 

Trismus, often called “lockjaw”, was originally linked to a disease known as tetanus. However, now it is characterised by restricted mouth opening due to joint dysfunction or muscle spasm controlled by the trigeminal nerve. This restriction can make it more difficult for a person to eat, speak, swallow and maintain oral hygiene. In cases that are much more severe, there is also an increased risk of choking. Trismus often lasts for a short time (up to two weeks), but in rare cases it may be permanent.¹

Causes and risk factors

Trismus can have various causes, but a sudden emergence of this condition is typically linked to injuries or trauma to the lower face and jaw. Trismus can also come from medical procedures such as anaesthesia administration or tooth extraction. When trismus happens this way, it usually resolves on its own and is temporary. However, when injuries are more severe, it can cause chronic trismus.¹ 

Chronic trismus can happen because of different disorders affecting the TMJ. Diseases in connective tissues, like lupus, are known contributors due to their impact on joint and muscle function. Treatment for head and neck cancer patients may also lead to trismus as a side effect, with recent studies showing that around 38%-42% of head and neck cancer patients developed trismus.²

Trismus can result from a wide variety of underlying health issues, and is commonly classified as follows:³

• Psychogenic (related to mental health)
• Neurogenic (related to the nerves)
• Iatrogenic (medical treatment)
• Dental problems
• Neoplasms (tumours)
• Traumatic
• Inflammatory
• Congenital malformation (birth defects)
• Infectious

Since trismus can happen in many cases, there are no clear patterns for when it might occur. The appearance of trismus usually depends on the root cause. As mentioned previously, trismus is commonly seen in individuals who receive radiation therapy for neck and head cancer. It may also occur in people with congenital conditions that affect jaw structure or function. In rare cases, trismus can even develop as a side effect of common illnesses such as a sore throat.^1,4

Signs and symptoms 

Trismus often comes with mild discomfort and pain. The normal mouth opening range is between 40-60mm (this is about two or three finger breadths). This measurement can vary from one person to another and may be influenced by gender, with males generally having a wider mouth opening. A maximum mouth opening that is less than 35mm is generally considered to be trismus.

When a person is suffering from trismus, they often do not realise that their jaw is the main problem. Instead, they may simply complain of pain or swelling in their teeth or face, depending on the cause. If a person with trismus has symptoms such as fever, weight loss or muscle spasm, the doctor may check for infections, nerve problems or cancer. A history of smoking or cancer may indicate that the trismus is cancer-related.

Trismus can also make it difficult for doctors to look inside the mouth and throat during medical check-ups. Doctors need to check the teeth, joints, gums, facial bones, neck and throat structures. They may also assess a person's speech, as certain infections that cause trismus can affect the voice.^1,5

Assessment and diagnosis

To identify trismus, healthcare providers begin by examining the patient's symptoms. Doctors may also use medical imaging tools to determine the underlying cause and assess any involvement of the TMJ. Computed tomography (CT) scans can reveal problems resulting from injuries, such as blood clots or damage to the bones of the face or jaw. Magnetic resonance imaging (MRI) scans can show the issues affecting the mouth or throat.^1,6 

Preventing trismus

People experiencing trismus should allow their jaw to relax and refrain from behaviours such as nail-biting or teeth grinding. Engaging in these habits can put stress on the jaw muscles and impede the recovery process. In some cases, it may be beneficial for a person to collaborate with a physical therapist. The therapist can assist with exercises designed to strengthen the jaw muscles.¹

Physical therapy for trismus

Physical therapy can help reduce jaw pain and improve jaw movement in people with trismus. When jaw movement is hard, simple acts such as eating and speaking can become difficult. However, the right therapy methods can help restore jaw function. Starting physical therapy early is important to prevent the condition from worsening, and a well-designed plan can be highly useful.  

Several physical therapy techniques may be used to treat trismus. Each method plays a specific role in relieving symptoms and restoring function. They include:

• Heat therapy
• Jaw stretching
• Massage therapy
• Medical devices

Heat therapy

One of the simplest yet most effective methods is heat therapy.  This involves applying a warm compress to the jaw area. By doing this, you help increase blood flow in your body and relax stiff muscles.  As a result, it becomes easier to perform jaw exercises. Heat therapy is usually used as a preparatory step before taking on other therapeutic exercises.⁷

Jaw stretching techniques 

Another important part of physical therapy is to stretch the jaw, whether done by yourself or with the help of a therapist. Slow stretching makes the jaw move better over time. Patients might use tools like a tongue depressor to slowly stretch their jaw, or they may even use their fingers to open their mouth incrementally. For best results, consistency is key.⁸

Massage therapy

Massage therapy can help ease tight muscles near the jaw joint. Massage techniques focused on the masseter and temporalis muscles will help relieve tension and reduce the pain. You can have a professional perform these massages or learn to do them at home. Physical therapists may also use manual techniques such as myofascial release to make jaw movement less painful.¹

Medical devices

Alongside hands-on techniques, patients may also use medical devices such as a jaw stretching tool to help with recovery. These devices aim to make sure patients keep stretching and opening their mouths more steadily. By using these physical techniques, individuals who have trismus may significantly improve their jaw function.⁹

Other treatment options for trismus

Besides physical therapy, pain relief medication such as non-steroidal anti-inflammatory drugs  (NSAIDS) can help reduce discomfort, whilst muscle relaxants can be used to ease muscle tightness. For pain that is more severe, corticosteroids may be used. 

In the case that these treatments are ineffective, surgery may be needed. Surgical options include procedures to repair the jaw or release tight muscles. Some individuals may find relief in alternative therapies such as acupuncture or transcutaneous electrical nerve stimulation (TENS), which uses mild electrical pulses to reduce pain and improve muscle function.^1,10,11

Summary

From this article, we learn that having trismus makes daily tasks hard. A person's ability to eat, speak and maintain oral hygiene becomes difficult. But the good news is, with the right treatment and therapy, trismus can be kept under control. Physical therapy techniques such as heat therapy, jaw stretching and massage therapy are good for relaxing the muscles and slowly bringing back function. Combining those treatments with medical devices made for trismus gives a clear path to achieve steady results. While physical therapy is the first step to handle trismus, in more difficult cases it is better to consider pain relief medication, muscle relaxants and even surgery. Starting treatment early and having a strong treatment plan is vital in stopping long-term issues. With this approach, living with trismus becomes much more manageable, allowing those with trismus to regain control of their own life.  

Trismus, also known as "lockjaw," is characterised by limited mouth opening due to issues with the jaw joint or muscle spasms. It can make eating, speaking, swallowing, and maintaining oral hygiene difficult, and in severe cases, increase the risk of choking. Trismus may last up to two weeks but can become permanent in rare cases. 

The condition generally arises from injuries to the lower face or jaw, particularly from trauma or medical procedures like tooth extractions. Chronic trismus can stem from disorders affecting the temporomandibular joint (TMJ), connective tissue diseases, or as a side effect of cancer treatments. 

Trismus is often accompanied by mild discomfort, with normal mouth opening ranging between 40-60mm. Symptoms can include pain, swelling, and difficulty for doctors in examining the mouth and throat during check-ups. To diagnose trismus, healthcare providers assess symptoms and may use imaging tools like CT or MRI scans to identify underlying issues. 

Preventing trismus involves relaxing the jaw and avoiding habits like teeth grinding. Physical therapy can improve jaw movement through techniques such as heat therapy, jaw stretching, massage, and the use of medical devices. Other treatment options include pain relief medications, muscle relaxants, and in some cases, surgical interventions or alternative therapies like acupuncture.