Proximal Hamstring Tendonopathy

ANSWER |  In this patient the most likely diagnosis is one of proximal hamstring tendinopathy (PHT). This is a common tendinopathy and cause of buttock pain. It is not as well recognised in the general medical community. It primarily affects athletes involved in running sports but can affect  less active individuals, usually perimenopausal women and older men, as well. Long distance runners are the primary cohort for this condition in the athletic population and it has a prevalence of approximately 10% in distance runners. The primary pathology is insertional tendinopathy of the proximal hamstring tendon(s), predominantly semimembranosus. This pain reduces the ability to sit for prolonged periods, and can impact athletic performance, especially in runners. PHT is often misdiagnosed due to the complex anatomy of the buttock region, referred pain from other structures and limited awareness of the injury. Potential differential diagnoses include lumbar referred pain or radiculopathy, ischiofemoral impingement, inferior pubic ramus bone stress,  sacroillitis or buttock soft tissue issues, including ‘ piriformis syndrome’.

On history the patient generally has well localized pain to the ischial tuberosity, and this is typically worsened by periods of prolonged sitting, especially on hard surfaces and particularly when driving. It is more likely to cause symptoms with walking up hills and stairs rather than on the flat, and running is typically the most provocative activity.

Examination findings may include pain on lumbar flexion. Double or single pelvic bridging may provoke pain, as may resisted knee flexion (hamstring curl), with associated weakness. Direct palpation to the ischial tuberosity may cause tenderness, but the degree can be underwhelming. Examination also needs to exclude other potential causes of buttock pain, including lumbar radiculopathy, sacroillitis or hip joint pathology.

Imaging may include plain Xray, ultrasound or MRI. Xray is a useful test to assess for degenerative hip or sacroiliac disease, pelvic stress fracture or unexpected nasty pathology. Ultrasound can demonstrate thickening or calcification of the proximal hamstring tendon, but does lack accuracy when compared to MRI. MRI is much better at demonstrating tendonopathy with associated partial tearing. It can also assess for other soft tissue abnormalities such as ischiofemoral impingement. The scan will also address possible bone or joint pathology such as a sacral or pelvic stress fracture or hip or SIJ degenerative change.