Introduction

Psoas syndrome (also referred to as iliopsoas syndrome) is one of the significant causes of hip and back pain. It is caused by injury to the iliopsoas muscle and is a rare syndrome that more commonly affects athletic individuals, such as dancers, runners, and athletes. The syndrome is underdiagnosed as it shares many symptoms with other musculoskeletal injuries and can only be checked by healthcare providers. It is important to understand psoas syndrome as it can be one of the diagnostic factors of hip pain.¹

Anatomy and function of the iliopsoas muscle

The iliopsoas muscle is comprised of the psoas muscle and iliacus muscle. Together these muscles form the main flexor of the hip and thigh. The psoas muscle is a long fusiform (spindle-like) muscle that lies over the vertebrae and meets the iliacus muscle at the distal end (at the furthest away). 

There are three main components of the iliopsoas muscle:

• Psoas major
• Psoas minor
• Iliacus muscle

These muscle components can function separately. The psoas major acts as a stabiliser for the femoral head, which is the part of the body that connects the pelvis with the femur (thigh bone). The psoas minor is involved in the flexion (bending of limb/joints) of the torso and control of the iliac fascia (a membrane covering the iliac muscle). The iliac muscle balances the pelvis region and controls hip flexion while walking or running.²

Role in hip movement and stability

• Primary flexor - The iliopsoas muscle is essential in hip flexion which is involved in everyday movements, such as walking, running or sitting.³
• Stabilisation - All three components of the iliopsoas muscle contribute to stabilising the lumbar spine, pelvis, and femur during movement. This maintains the body’s posture and balance.³
• Impact on spinal alignment - Since the psoas muscle is attached to the lumbar spine, it is also involved in the spinal alignment and functions.³

Understanding psoas syndrome

Psoas syndrome is a term used interchangeably with internal snapping of the hip, iliopsoas tendinitis or iliopsoas impingement. It is caused by injury or damage to the iliopsoas muscle, usually due to overusing the muscle during exercise or weakness of the muscles in the hip (gluteal muscles).⁴ 

It commonly presents as hip and groin pain resulting from repetitive actions or exercises using hip flexion movement. For this reason, the syndrome is known as the dancer's hip or jumper hip. It commonly occurs in runners, dancers and athletes but can also be seen in the general population or individuals with impaired or inflammatory arthritis.¹

Causes and risk factors

Psoas syndrome can be caused by:¹

• Overuse or strain of iliopsoas muscle 
• Iliopsoas muscle injury or trauma
• Repetitive and intense exercises involving hip flexion
• Poor posture such as slouching
• Prolonged sitting 
• Pre-existing musculoskeletal conditions
• Post-surgical complications  

Symptoms and clinical presentation

Symptoms of psoas syndrome include:¹

• Lower back and hip pain - the location of the pain can also be described as pelvic pain, buttock pain or groin pain and can spread to the surrounding area.
• Snapping feeling in the groin when the knee is flexed to 90 degrees
• Difficulty in walking
• Struggling to change position from sitting to standing and vice versa
• Restricted range of motion
• Muscle spasms in the hip or lower back region
• Limping or shuffling gait
• Tightness or palpitation of hip flexor muscles    

Epidemiology

The frequency and occurrence of the psoas syndrome in the general population is unknown. The incidence is significantly higher in athletes. In particular, athletes who are assigned female at birth (AFAB) have a higher chance of developing the psoas syndrome compared to those assigned male at birth (AMAB). People with pre-existing hip disorders are also more likely to get the disease, however, psoas syndrome is uncommon in elderly patients.¹

Diagnosis of psoas syndrome

Medical history and physical examination

A comprehensive medical history is essential in determining the potential risk factors such as pre-existing musculoskeletal conditions. Physical examinations such as muscle palpation help to detect the specific area of pain and range of motion assessments are necessary. Specialised tests for the Psoas sign and Ludloff sign may also be performed.¹ 

Imaging techniques are also used to diagnose psoas syndrome. Although X-rays are not typically diagnostic for psoas syndrome, they are useful in ruling out other hip region disorders such as fractures and arthritis. Ultrasound can provide a differential diagnosis of the origins of hip pain. Magnetic resonance imaging (MRI) can provide the visualisation of muscle inflammation, oedema or structural abnormalities.¹

Differential diagnosis with other hip pathologies

One of the reasons why iliopsoas syndrome is underdiagnosed is that it shares many symptoms with other hip and lumbar spine disorders, such as:

• Hip osteoarthritis
• Lumbar disc herniation (slipped disc)
• Hip joint dysfunction

Visceral causes such as appendicitis and colon cancer can present similar symptoms to psoas syndrome. Therefore differential diagnosis is essential to rule out other potential causes of hip pain.¹

Treatment options

Conservative management

The primary treatment of psoas syndrome starts with conservative management (avoidance of invasive procedures such as surgery).

Rest and activity modification

Since the underlying cause of the psoas syndrome is muscle overuse and trauma, it is important to avoid intensive activities, such as prolonged sitting, high-impact exercises and movements requiring repetitive hip flexion.¹ 

Physical therapy

It is recommended to follow a structured physical therapy programme focusing on stretching and muscle-strengthening exercises to improve flexibility and core stability. One study found that the exercise programme was effective for 100% of injured dancers.⁵

Heat and cold therapy

Applying heat and cold packs to the affected area can relieve pain and inflammation.² 

Medication

Over-the-counter anti-inflammatory medications, such as ibuprofen or naproxen can be prescribed to alleviate pain and inflammation associated with psoas syndrome.⁶

Interventional procedures

Trigger point injections

Injection of local anaesthetic or corticosteroid into trigger points within the psoas muscle can relieve pain and muscle spasms, which enables rehabilitation. The administration of these injections is guided by ultrasound and can be used as both therapeutic and differential diagnostic for hip pain.⁷

Nerve blocks

The injection of selective nerve blocks guided by MR is currently in the trial stage. Targeting the femoral nerve or genitofemoral nerve (which passes through the psoas major) can provide temporary pain relief. This helps to identify the source of pain originating from the psoas muscle or adjacent structures.⁸

Surgical interventions

Although surgical intervention is rare in psoas syndrome treatment, it can be utilised in case of severe symptoms or structural abnormalities. One of the surgical treatments is arthroscopic lengthening of the tendon.² 

Complications

• If psoas syndrome is left untreated, it can cause chronic pain which can significantly impact daily activities and quality of life.
• It can cause muscle imbalance and reduce the range of motion in the hip and lumbar spine (lower end of the spine).
• Inflammation of the psoas muscle can cause compression on adjacent nerves, leading to the symptoms of sensory disturbances and pain.
• The prolonged duration of the syndrome can cause postural abnormalities, i.e., rigid body movements and chronic positioning of the body.
• Recurrent inflammation of the iliopsoas tendon.
• Mistakes during the treatment of corticosteroid injections can lead to nerve damage.¹  

Prevention strategies

There are several ways to prevent psoas syndromes:²

Maintain a good posture

Practise good posture whilst sitting, standing, and walking to minimise the strain on the psoas muscle and promote spinal alignment. Support pillows and towels can be used while sitting and lying down to maintain a neutral spine position. 

Regular stretching and muscle-strengthening exercises

Perform regular stretching exercises to prevent muscle tightness and improve muscle flexibility. Strengthening exercises are also important to improve core and gluteal muscles, lessening the reliance on the psoas muscle.

Gradual increase in intensity and duration of exercises

Avoiding sudden increases in activities such as running and cycling and allowing the body to adapt gradually will prevent injuries to the psoas muscle.

Maintain healthy body weight

An increase in body weight can put stress on the back and hip muscles. Therefore, it is important to have a balanced diet and regular exercise to maintain healthy body weight.

Seek professional guidance

Consulting with a physical therapist or exercise specialist is essential in developing a personalised exercise. Regular monitoring and adjustments can reduce the risks before the injury occurs.

Summary

Although psoas syndrome is a rare disorder among musculoskeletal disorders, it can have a significant impact on daily activities. It starts with an injury to the iliopsoas muscle and presents with hip and back pain. Although it mostly occurs in athletes, it can also happen in the general population, especially in individuals with previous muscle and joint injuries around the hip region. To prevent the syndrome multiple risk factors, such as intensive exercises, prolonged sitting, and poor posture need to be considered. There are several treatments available, such as physical therapy, pain relief medications, and corticosteroid injections. If left untreated, it can lead to severe chronic symptoms, muscle imbalance, and compression of the adjacent nerves. However, by emphasising preventive strategies, such as regular exercise and self-care, individuals can reduce the risk of developing psoas syndrome and other related musculoskeletal disorders.