If you are here at OsteoporosisConnection.com you are aware of osteoporosis, osteopenia and some of the other metabolic bone disorders; like osteogenesis imperfecta, osteomalacia, idiopathic juvenile osteoporosis and others, but you may not have heard of transient migratory osteoporosis (TMO) since it's not that common or discussed that often. We hope to change that by explaining what it is, how it's diagnosed.
and how it's treated,
Transient migratory osteoporosis is not a new form of a metabolic bone disorder; in fact it's been in the medical literature for over fifty years.
Definition of transient migratory osteoporosis: A form of transient regional osteoporosis manifested by rapidly developing, self-limiting, and reversible osteoporosis affecting periarticular bone without clear evidence of any precipitating event, such as trauma or immobilization. The knee, ankle, foot and hip are affected most commonly. Local pain and swelling, particularly in the lower extremity, develop rapidly but then diminish and disappear, to be followed by similar involvement in other regions of the same or opposite extremity. Usually the joint nearest to the diseased one is the next to be involved. In some patients only a portion of a joint may be affected. The joint space is maintained, and no intra-articular erosion is seen, although bone scans show increased activity in involved areas. This disorder may be closely related to reflex sympathetic dystrophy and transient osteoporosis of the hip (Medcyclopaedia; GE Health Care 2011). 
What is transient migratory osteoporosis?
TMO is a disorder that usually resolves within three to nine months; and generally occurs in middle age men and women in their third trimester of pregnancy. However, it is possible for patients not in these two groups - middle age men and pregnant women - to acquire this disorder.
The onset of pain starts over several weeks to months from its commencement. It's important to distinguish this from osteonecrosis or osteomyelitis which requires more aggressive management.
Symptoms would include pain, bone marrow swelling and migratory problems in opposite joints.
What are the diagnostic criteria for transient migratory osteoporosis (TMO)?
When diagnosing this disorder the clinician will order plain radiographic x-rays and a MRI. When doing an MRI, they are looking for swelling (edema) in the bone marrow. Plain x-rays may show regional osseous demineralization (a loss of minerals in the bone) indicative of osteopenia/osteoporosis. The MRI determines bone marrow swelling.
Where does TMO usually present?
TMO is usually found in the hip, ankle, foot and knee. We currently don't understand why this happens because the cause is unknown. TMO also moves from one joint to another, once the origininating joint heals. If you had this disorder in your hip, and it heals, it generally moves to the opposite hip. The same would apply for foot, ankle and knee.
How do we treat TMO?
TMO is similar to osteoporosis because bisphosphonates may be used in rare cases, but it usually resolves with conservative treatment, which includes joint protectors. However, most cases of TMO resolve completely with no pharmaceutical treatment.
How does TMO differ from osteoporosis?
In TMO the problem migrates from one joint to another over a short period of time and then resolves in most cases. Osteoporosis does not resolve this way nor does it migrate from one joint to another. Also, bone marrow edema is not a problem seen in osteoporosis as it is in TMO. Pain is not a hallmark of osteoporosis until there is a fracture unlike the pain seen in TMO. Unlike TMO, osteoporosis is diagnosed with a DXA scan instead of the x-rays and MRI used in TMO.
MRI Images showing hip edema:
Arrow points to hip edema Edema resolving after 3 months
We hope this helps to explain this little-known bone and joint disorder known as transient migratory osteoporosis.
- Medcyclopaedia Standard Edition; Retrieved May 15, 2011 http://www.medcyclopaedia.com/library/topics/volume_iii_1/r/regional_migratory_osteoporosis.aspx
- X-ray images of TMO; Transient Osteoporosis of the Hip; McWalter P, Hassan A. Ann Saudi Med. 2009 Mar-Apr; 29(2):146-8. http://www.ncbi.nlm.nih.gov/pubmed/19318749