Entheses are the sites at which tendons or ligaments attach to bone. Inflammation of entheses is known as 'enthesitis', whereas the term 'enthesopathy' has a broader meaning and can encompass all pathological disorders related to these insertions.

Enthesopathy is multifactorial, but frequently degnerative in aetiology, as entheses are points of high mechanical stress and subject to repeated microtrauma.

Clinical course

Patients with enthesopathy commonly present with pain, stiffness and tenderness aggravated by exercise. In general, it has a chronic course, sometimes causing long-term musculoskeletal pain and is associated with local calcification and ossification.

Accurate clinical assessment of enthesopathy can be challenging. Radiological investigations, in the form of MRI and ultrasound, are highly sensitive in the detection of enthesopathy.

Degenerative enthesopathy 

Degenerative enthesopathy is well described at various sites, in particular:

• Supraspinatus insertion on the greater tuberosity of the humerus
• Achilles tendon insertion on the calcaneum
• Common extensor origin on the lateral epicondyle of the elbow
• Gluteal tendon insertion onto the greater trochanter. Around the hip, this manifests as greater trochanteric pain syndrome often referred to as trochanteric bursitis.

However, gluteus maximus tendinopathy or enthesopathy is less frequently described with only a few articles in the literature discussing the CT appearances of this unusual condition.

Anatomy

The gluteus maximus is the largest and most superficial of the three gluteal muscles. It acts to extend and assist lateral rotation of the thigh, in particular between the flexed and standing positions (such as when rising from sitting).

Gluteus maximus originates from the ilium posterior to the posterior gluteal line, sacrotuberous ligament, dorsal surface of sacrum and coccyx (Figure 1). Its insertions are entirely separate from the gluteus minimus and medius insertions, which insert onto the greater trochanter (Figure 2). The maximus muscle fibres insert both into the iliotibial tract (Figure 3) as well as a discrete tendinous insertion onto the gluteal tuberosity of the posterior femur (Figures 4,5). 

It is innervated by the inferior gluteal nerve, which arise from the sacral plexus.