Transient osteoporosis of the hip (TOH) is a rare condition that can cause a sudden onset of pain and reduced movement in the hip. Its name refers to the fact that it is often temporary, resolving on its own or with conservative treatment.

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The exact prevalence of TOH is not fully clear, and doctors can mistake it for other conditions, often delaying a diagnosis. However, 2017 research focusing on pregnant females, who have an increased risk of TOH, estimates that it affects 1 in 250,000 of these individuals.

This article explores TOH in more detail, looking at the symptoms, causes, risk factors, diagnosis, and treatment options. It also lists the other parts of the body that transient osteoporosis can affect.

TOH is a rare but often temporary condition that causes a loss of bone density in part of the hip joint, known as the femoral head. The condition can have a sudden onset, but with a prompt diagnosis and effective treatment, it often resolves within 6–12 months.

Another type of osteoporosis is age-related osteoporosis, which typically develops after the age of 50 years. It occurs as bone loss speeds up and starts to outpace bone formation.

Unlike TOH, age-related osteoporosis manifests gradually and causes bone weakness across the body. It is also far more common than TOH. The Centers for Disease Control and Prevention (CDC)Trusted Source estimate that osteoporosis affects 20% of females aged 50 years and older and 5% of males in the same age group.

Symptoms

The symptoms of TOH tend to have a sudden onset and can include:

  • pain in the hip that can extend to the groin, buttocks, and front of the thigh
  • slightly restricted movement when trying to do larger movements involving abduction or rotation of the hips
  • pain that worsens when weight-bearing and at night but improves with rest
  • a noticeable limp when walking
  • pain that gradually increases and lasts for weeks or months

Often, the pain occurs on only one side of the hips. However, in roughly 25–30% of cases, pain occurs on both sides.

Experts still do not know the exact cause of TOH. However, they have several theoriesTrusted Source, including:

A 2020 paperTrusted Source uses a case study to explore how endocrine factors, such as subclinical hypothyroidism, may relate to TOH.

Subclinical hypothyroidism occurs when a person has an elevated level of thyroid stimulating hormone, but their levels of thyroid hormones are still within an expected range.

In more severe cases, subclinical hypothyroidism can turn into hypothyroidism. It may also resolve without treatment in milderTrusted Source subclinical forms, so doctors often adopt a “wait-and-see strategy.”

The symptoms of subclinical hypothyroidism can include:

The study authors theorize that subclinical hypothyroidism may act as a metabolic trigger, influencing the amount of fat in the bone marrow cavity and contributing to TOH onset. It may also cause inflammation in the body and changes in blood flow.

The authors of a 2017 studyTrusted Source note that TOH is three times more likely to affect males than females.

A 2020 study reports that middle-aged males and pregnant people are the most at risk of TOH.

More recent researchTrusted Source into TOH and pregnancy has found that TOH is most common among pregnant people in their last trimester and those in the postpartum period.

There are also potential secondary risk factors for TOH, including:

A doctor will begin the diagnostic process by asking about a person’s medical history, including any possible injuries to the affected area. They will then carry out a physical examination in which they will move the person’s hip to determine their range of motion. They will also ask the person to move their hip themselves and bear weight on the affected side.

Key signs of TOH are severe pain when weight-bearing and worse pain when the person is moving their hip themselves.

Further testing for TOH usually involves imaging scans to obtain a detailed look at the hip joint. X-ray, CT, and MRI scans may show a small decrease in bone density in the femoral head at the top of the hip.

MRI scans may also detect an abnormality called bone marrow edema, a common finding in cases of TOH. Bone marrow edema occurs when the bone marrow, a spongy tissue present inside most bones, becomes filled with liquid.

Although no blood tests can directly diagnose TOH, a doctor may order some to rule out other possible causes, such as:

  • hormonal disorders
  • nutritional disorders
  • cancer

Treatment for TOH aims to limit damage to the joint, manage discomfort, and speed up recovery.

Medications

Doctors may prescribe medications to relieve pain and control inflammation. These may include:

Evidence from 2019Trusted Source suggests that bisphosphonates may speed up the recovery process, potentially due to their anti-inflammatory properties and their ability to inhibit osteoclasts, which are cells that break down bone.

A doctor may also suggest taking vitamin D and calcium supplements to help promote bone regrowth.

Conservative treatment

Conservative treatment of TOH will also involve resting and avoiding weight-bearing activities. Physical therapy can help preserve the range of movement in the hip and help build up muscles around the joint during recovery.

Conservative treatment with NSAIDs or supplementation may avoid further damage, speed up the healing process, and shorten recovery time.

Surgery

Core decompression surgery is an additionalTrusted Source option in cases where medications have been ineffective. People who undergo this treatment usually recover faster than those receiving conservative therapy.

A 2020 paperTrusted Source also investigated the recovery times of people who followed a more conservative treatment and those who chose a surgical route. Researchers found that those who underwent surgery had a faster recovery time with a lower recurrence rate.

Although transient osteoporosis most commonly occurs in the hip, some 2016 research suggests that it can also occur in the:

  • knee
  • ankle
  • foot

Case reports confirm that it can affect these areas in pregnant people.

A 2019 paper reporting on a case of transient bone marrow edema of the foot in a 12-year-old suggests that there may be a link between the condition and vitamin D deficiency.

Although TOH can be a debilitating condition, the outlook for people who experience it is generally very positive. It is often a self-limiting condition that resolves within 6–12 months. In rare cases, TOH may recur later in life — in either the same hip or the opposite one.

TOH is a rare condition that can cause a sudden onset of pain and result in a loss of bone density in part of the hip joint.

TOH is more likely to affect pregnant people, middle-aged males, and those with certain risk factors, such as smoking or high alcohol consumption. Vitamin D deficiency may also contribute to the condition developing.

However, with a prompt diagnosis and suitable treatment, the symptoms often resolve within 6–12 months.