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Regional migratory osteoporosis: a case report
J Orthop Sci (2004) 9:178–181 DOI 10.1007/s00776-003-0758-z
Regional migratory osteoporosis: a case report Keisuke Horiuchi1, Nobuyuki Shiraga2, Nobuyuki Fujita1, Masaaki Yamagishi3, and Hiroo Yabe1 1
Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan Department of Radiology, Keio University School of Medicine, Tokyo, Japan 3 Department of Orthopedic Surgery, Tachikawa Hospital, Tachikawa, Japan 2
Abstract We describe a case of regional migratory osteoporosis (RMO) with clinical images clearly illustrating the migratory behavior of this unusual disorder. RMO is a relatively rare disorder that manifests as rapidly developing, selflimiting, reversible osteoporosis typically seen in the lower limbs of middle-aged men. In our case, the lesion was observed migrating not only from the knee to the ankle within the same limb but also within two compartments of the same knee. To our knowledge, this is the first case showing migration of a lesion both within the same joint and to the adjacent joint. We also present computed tomography images showing characteristic spotty bone defects that are rarely described in the literature, along with magnetic resonance imaging scans revealing bone marrow edema in the affected region. Although little is understood about the etiology or treatment of RMO, knowledge of this disorder is mandatory to avoid its misdiagnosis as some other, more aggressive disease, leading to unnecessary treatment. Key words Regional migratory osteoporosis · Transient osteoporosis · Differential diagnosis
Introduction Regional migratory osteoporosis (RMO), also described as transient osteoporosis and transient bone marrow edema syndrome, is an uncommon self-limited condition with unknown etiology. RMO has a predilection for middle-aged men and frequently affects the knee, ankle, or foot.2,8 Recurrence of the symptoms in joints adjacent to the primary site is a distinctive feature of this disorder. RMO may be closely related to transient osteoporosis of the hip (TOH), which is most commonly seen in pregnant women during their third
Offprint requests to: K. Horiuchi Received: August 28, 2003 / Accepted: December 9, 2003
trimester,1 and reflex sympathetic dystrophy (RSD), which is commonly preceded by minor trauma. Because the initial presentation of RMO usually lacks specific symptoms, patients with this disorder may be unintentionally neglected or misdiagnosed, especially when the radiographs fail to show any objective findings. The diagnosis is one of exclusion, and careful observation is required to address this disorder properly. Here we present a case of RMO with illustrative clinical images, which we believe can serve as an excellent clinical reference when one encounters this disorder during daily clinical practice.
Case report A 53-year-old man presented with a 5-week history of right knee pain. He had no history of trauma or any systemic disorder that might have caused pain in the joints. On physical examination, tenderness and slight effusion was found in the right knee. Plain radiographs revealed minimal bone atrophy in the lateral femoral condyle (Fig. 1A,B). There were no significant degenerative changes in the knee, and the joint space was maintained. There was a slight increase in the white blood cell count, but other laboratory findings, including C-reactive protein and rheumatoid factor, were within normal limits. To investigate the nature of the bone atrophy and the knee pain, we performed further clinical imaging examinations. A radionuclide bone scan showed increased activity in the right knee (Fig. 1C). Magnetic resonance imaging (MRI) revealed high signal intensity on T2weighted images in the lateral femoral condyle, suggestive of bone marrow edema (Fig. 1D). Joint effusion was also found on MRI. The patient was treated conservatively with nonsteroidal antiinflammatory drugs and rest. The pain gradually worsened, however, and bone atrophy became
K. Horiuchi et al.: Regional migratory osteoporosis
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Fig. 1. Radiographs of the right (A) and left (B) knees at presentation. Slight bone atrophy in the lateral femoral condyle is noted. C Radionuclide bone scan reveals uptake in the lateral condyle of the right knee. D Magnetic resonance imaging (MRI) of the right knee 1 month after the initial presentation. Note the bone marrow edema in the lateral femoral condyle as well as soft tissue edema. E, F Radiographs of the right knee 4 months after the onset. Significant bone
atrophy is observed. G MRI scan of the right knee obtained 4 months after the onset. The edematous lesion had moved from the lateral condyle to the medial condyle. H, I Computed tomography (CT) images of the right (H) and left (I) condyle. Numerous spotty bone defects and soft tissue swelling are evident in the right knee. J MRI scan of the right knee obtained 7 months after the onset. Bone marrow edema in the knee has almost disappeared
evident on plain radiographs (Fig. 1E,F). Repeat MRI performed 3 months after the initial MRI revealed migration of the edematous lesion from the lateral femoral condyle to the medial femoral condyle (Fig. 1G).
Computed tomography (CT) images showed numerous spotty bone defects around the knee joint, including the patella, indicative of rapidly progressing bone resorption (Fig. 1H,I).
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K. Horiuchi et al.: Regional migratory osteoporosis
Fig. 2. Radiographs of the right (A) and left (B) ankles. Bone atrophy is evident compared to the unaffected left ankle, especially in the talus. CT image of the right (C) and left (D) ankles. Numerous spotty bone defects and soft tissue swelling
are evident in the right ankle. E MRI scan of the right ankle. Note the bone marrow edema in the talus and effusion in the joint
The pain in the right knee abated 7 months after its onset, preceded by the disappearance of clinical findings, including swelling and joint effusion. The bone marrow edema found during the previous MRI examinations had also disappeared by that time (Fig. 1J). This asymptomatic period was brief, however. One month after recovery from the right knee pain, the patient developed a mild effusion and pain in the right ankle that worsened with ambulation. Radiographs revealed extensive bone atrophy around the right ankle joint (Fig. 2A,B). The results of MRI and CT examinations of the ankle joint were consistent with that of the knee, showing bone marrow edema and extensive bone loss (Fig. 2C–E). The patient continued on conservative treatment and eventually recovered spontaneously 6 months after the initial onset of pain in the right ankle. Although the bone atrophy seen on plain radiographs remained, the patient is currently well without any symptoms 1 year after recovery from the right ankle pain.
formative. On physical examination, there is often severe pain and swelling in the affected joint. As the disease develops, bone atrophy in the affected joint becomes evident, although the joint space is maintained throughout the course of the disorder. Increased uptake in the affected joint can be seen with radionuclide bone scan before plain radiography reveals any abnormalities. On MRI scans there are low signal intensity on T1-weighted images and high signal intensity on T2weighted images in the bone marrow of the affected joint, consistent with bone marrow edema.11 In addition, an effusion is usually seen in the joint space. The diagnostic value of CT scan has not been discussed in the literature,4,7 but as shown in this report CT images with numerous spotty defects (without the presence of apparent cortical thinning) are distinct from those of generalized osteoporosis or local osteolytic lesions due to malignant metastasis. They therefore may be helpful for distinguishing RMO from other conditions. The feature that most distinguishes RMO from other disorders is its characteristic migratory behavior and self-limited nature, which can be confirmed by repeated bone scans or MRI examinations,1,16 although it can be confirmed only retrospectively. Hence the diagnosis must be made after careful follow-up and by ruling out more common diseases, such as gout, rheumatoid arthritis, infectious arthritis, primary or metastatic malignancy, tuberculosis, osteomyelitis, disorders of calcium metabolism, and aseptic necrosis.1,7 Our case had, in all respects, a typical clinical presentation and course. The patient was male and in his fifties, with no contributory history. The pain in the right knee started without any particular event, worsened rapidly, and disappeared afterward only to be followed by pain in the right ankle. At the initial presentation, the patient exhibited no specific symptoms; however, slight bone atrophy and effusion in the right knee joint
Discussion Regional migratory osteoporosis is an uncommon, selflimited, clinical entity of unknown etiology.1,2 Possibly due to its rarity and the lack of specific clinical symptoms, the disorder might not be widely recognized. However it is important to distinguish it from other, more aggressive diseases, as spontaneous recovery seems to be the rule for RMO. Regional migratory osteoporosis affects the lower limbs of middle-aged men, usually with no preceding event. Because there is a delay between the onset of the symptoms and the appearance of objective findings on the usual radiographs, early diagnosis may be difficult. Routine laboratory examinations are typically unin-
K. Horiuchi et al.: Regional migratory osteoporosis
led us to investigate further. We then observed bone marrow edema in the femoral condyle and later migration of the lesion. We were thus able to confirm the diagnosis. In our case, we found migration of bone marrow edema within different compartments of the same joint. To our knowledge, this observation has been reported in only five cases in the literature,3,6,10,16,17 although this phenomenon may not be as rare as previously thought.6 Because this condition can be observed only when clinical imaging evaluations (radionuclide bone scans or MRI) are performed rather frequently, the migratory behavior in the same affected joint may simply be overlooked. Nevertheless, this report may be the first to show migration of the lesion both within the same joint and to another joint. The etiology of RMO remains obscure. Several investigators have proposed a hypothesis that prolonged or exaggerated activation of a large number of bone turnover foci caused by a microfracture may contribute to the occurrence of transient osteoporosis.5,8,12 Moreover, recent studies suggesting a possible association of RMO with systemic osteoporosis may support this hypothesis.9,13 Because RMO affects weight-bearing lower limbs and is not seen in young adults, this indeed seems to be a rational explanation. Still, this hypothesis does not fully explain why the disorder mainly affects middle-aged men but not postmenopausal women, in whom there is a more severe and rapid decrease in bone density. It is likely, then, that there are unknown factors contributing to the occurrence of RMO other than an accumulation of microfractures. Recent studies showed the efficacy of intravenous pamidronate for the treatment of both TOH15 and RSD.14 Given that RMO is, in fact, closely related to either or both of these disorders (i.e., it shares a common pathological mechanism in the process of bone resorption), this drug may also have beneficial effects on RMO as well. At any rate, RMO is a self-limited disorder, and each separate lesion usually recovers spontaneously 6–9 months after the onset.1 Hence treatment other than analgesics and protected weightbearing is not necessarily required.
Conclusions We present a case of RMO clearly showing its migratory behavior both within the initially affected joint (right knee) and into the adjacent joint (right ankle). The diagnostic value of MRI, radionuclide bone scan,
181
and plain radiography is well established; and CT scans may be helpful for the differential diagnosis, as shown in this report. With its rare occurrence and unspecific clinical symptoms, RMO may be overlooked or misdiagnosed. With close observation and, most importantly, knowledge of this disease, both clinician and patient can be spared extra trouble. Acknowledgment. We thank Kristie Kelly and Mari Ishii for critically reading the manuscript.
References 1. Banas MP, Kaplan FS, Fallon MD, et al. Regional migratory osteoporosis: a case report and review of the literature. Clin Orthop 1990;250:303–9. 2. Duncan H, Frame B, Frost H, et al. Regional migratory osteoporosis. South Med J 1969;62:41–4. 3. Fertakos RJ, Swayne LC, Colston WC. Three-phase bone imaging in bone marrow edema of the knee. Clin Nucl Med 1995;20:587–90. 4. Froberg PK, Braunstein EM, Buckwalter KA. Osteonecrosis, transient osteoporosis, and transient bone marrow edema: current concepts. Radiol Clin North Am 1996;34:273–91. 5. Frost HM. Perspectives: bone’s mechanical usage windows. Bone Miner 1992;19:257–71. 6. Gaeta M, Mazziotti S, Minutoli F, et al. Migrating transient bone marrow edema syndrome of the knee: MRI findings in a new case. Eur Radiol 2002;12:S40–2. 7. Guerra JJ, Steinberg ME. Distinguishing transient osteoporosis from avascular necrosis of the hip. J Bone Joint Surg Am 1995; 77:616–24. 8. Langloh ND, Hunder GG, Riggs BL, et al. Transient painful osteoporosis of the lower extremities. J Bone Joint Surg Am 1973;55:1188–96. 9. Mavichak V, Murray TM, Hodsman AB, et al. Regional migratory osteoporosis of the lower extremities with vertebral osteoporosis. Bone 1986;7:343–9. 10. Parker RK, Ross GJ, Urso JA. Transient osteoporosis of the knee. Skeletal Radiol 1997;26:306–9. 11. Tannenbaum H, Esdaile J, Rosenthall L. Joint imaging in regional migratory osteoporosis. J Rheumatol 1980;7:237–44. 12. Trevisan C, Ortolani S. Bone loss and recovery in regional migratory osteoporosis. Osteoporos Int 2002;13:901–6. 13. Trevisan C, Ortolani S, Monteleone M, et al. Regional migratory osteoporosis: a pathogenetic hypothesis based on three cases and a review of the literature. Clin Rheumatol 2002;21:418–25. 14. Varenna M, Zucchi F, Ghiringhelli D, et al. Intravenous clodronate in the treatment of reflex sympathetic dystrophy syndrome: a randomized, double blind, placebo controlled study. J Rheumatol 2000;27:1477–83. 15. Varenna M, Zucchi F, Binelli L, et al. Intravenous pamidronate in the treatment of transient osteoporosis of the hip. Bone 2002;31: 96–101. 16. Wambeek N, Munk PL, Lee MJ, et al. Intra-articular regional migratory osteoporosis of the knee. Skeletal Radiol 2000;29:97– 100. 17. Yamasaki S, Masuhara K, Miki H, et al. Three cases of regional migratory osteoporosis. Arch Orthop Trauma Surg 2003;123:439– 41.
Regional migratory osteoporosis: a case report Keisuke Horiuchi1, Nobuyuki Shiraga2, Nobuyuki Fujita1, Masaaki Yamagishi3, and Hiroo Yabe1 1
Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan Department of Radiology, Keio University School of Medicine, Tokyo, Japan 3 Department of Orthopedic Surgery, Tachikawa Hospital, Tachikawa, Japan 2
Abstract We describe a case of regional migratory osteoporosis (RMO) with clinical images clearly illustrating the migratory behavior of this unusual disorder. RMO is a relatively rare disorder that manifests as rapidly developing, selflimiting, reversible osteoporosis typically seen in the lower limbs of middle-aged men. In our case, the lesion was observed migrating not only from the knee to the ankle within the same limb but also within two compartments of the same knee. To our knowledge, this is the first case showing migration of a lesion both within the same joint and to the adjacent joint. We also present computed tomography images showing characteristic spotty bone defects that are rarely described in the literature, along with magnetic resonance imaging scans revealing bone marrow edema in the affected region. Although little is understood about the etiology or treatment of RMO, knowledge of this disorder is mandatory to avoid its misdiagnosis as some other, more aggressive disease, leading to unnecessary treatment. Key words Regional migratory osteoporosis · Transient osteoporosis · Differential diagnosis
Introduction Regional migratory osteoporosis (RMO), also described as transient osteoporosis and transient bone marrow edema syndrome, is an uncommon self-limited condition with unknown etiology. RMO has a predilection for middle-aged men and frequently affects the knee, ankle, or foot.2,8 Recurrence of the symptoms in joints adjacent to the primary site is a distinctive feature of this disorder. RMO may be closely related to transient osteoporosis of the hip (TOH), which is most commonly seen in pregnant women during their third
Offprint requests to: K. Horiuchi Received: August 28, 2003 / Accepted: December 9, 2003
trimester,1 and reflex sympathetic dystrophy (RSD), which is commonly preceded by minor trauma. Because the initial presentation of RMO usually lacks specific symptoms, patients with this disorder may be unintentionally neglected or misdiagnosed, especially when the radiographs fail to show any objective findings. The diagnosis is one of exclusion, and careful observation is required to address this disorder properly. Here we present a case of RMO with illustrative clinical images, which we believe can serve as an excellent clinical reference when one encounters this disorder during daily clinical practice.
Case report A 53-year-old man presented with a 5-week history of right knee pain. He had no history of trauma or any systemic disorder that might have caused pain in the joints. On physical examination, tenderness and slight effusion was found in the right knee. Plain radiographs revealed minimal bone atrophy in the lateral femoral condyle (Fig. 1A,B). There were no significant degenerative changes in the knee, and the joint space was maintained. There was a slight increase in the white blood cell count, but other laboratory findings, including C-reactive protein and rheumatoid factor, were within normal limits. To investigate the nature of the bone atrophy and the knee pain, we performed further clinical imaging examinations. A radionuclide bone scan showed increased activity in the right knee (Fig. 1C). Magnetic resonance imaging (MRI) revealed high signal intensity on T2weighted images in the lateral femoral condyle, suggestive of bone marrow edema (Fig. 1D). Joint effusion was also found on MRI. The patient was treated conservatively with nonsteroidal antiinflammatory drugs and rest. The pain gradually worsened, however, and bone atrophy became
K. Horiuchi et al.: Regional migratory osteoporosis
179
Fig. 1. Radiographs of the right (A) and left (B) knees at presentation. Slight bone atrophy in the lateral femoral condyle is noted. C Radionuclide bone scan reveals uptake in the lateral condyle of the right knee. D Magnetic resonance imaging (MRI) of the right knee 1 month after the initial presentation. Note the bone marrow edema in the lateral femoral condyle as well as soft tissue edema. E, F Radiographs of the right knee 4 months after the onset. Significant bone
atrophy is observed. G MRI scan of the right knee obtained 4 months after the onset. The edematous lesion had moved from the lateral condyle to the medial condyle. H, I Computed tomography (CT) images of the right (H) and left (I) condyle. Numerous spotty bone defects and soft tissue swelling are evident in the right knee. J MRI scan of the right knee obtained 7 months after the onset. Bone marrow edema in the knee has almost disappeared
evident on plain radiographs (Fig. 1E,F). Repeat MRI performed 3 months after the initial MRI revealed migration of the edematous lesion from the lateral femoral condyle to the medial femoral condyle (Fig. 1G).
Computed tomography (CT) images showed numerous spotty bone defects around the knee joint, including the patella, indicative of rapidly progressing bone resorption (Fig. 1H,I).
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K. Horiuchi et al.: Regional migratory osteoporosis
Fig. 2. Radiographs of the right (A) and left (B) ankles. Bone atrophy is evident compared to the unaffected left ankle, especially in the talus. CT image of the right (C) and left (D) ankles. Numerous spotty bone defects and soft tissue swelling
are evident in the right ankle. E MRI scan of the right ankle. Note the bone marrow edema in the talus and effusion in the joint
The pain in the right knee abated 7 months after its onset, preceded by the disappearance of clinical findings, including swelling and joint effusion. The bone marrow edema found during the previous MRI examinations had also disappeared by that time (Fig. 1J). This asymptomatic period was brief, however. One month after recovery from the right knee pain, the patient developed a mild effusion and pain in the right ankle that worsened with ambulation. Radiographs revealed extensive bone atrophy around the right ankle joint (Fig. 2A,B). The results of MRI and CT examinations of the ankle joint were consistent with that of the knee, showing bone marrow edema and extensive bone loss (Fig. 2C–E). The patient continued on conservative treatment and eventually recovered spontaneously 6 months after the initial onset of pain in the right ankle. Although the bone atrophy seen on plain radiographs remained, the patient is currently well without any symptoms 1 year after recovery from the right ankle pain.
formative. On physical examination, there is often severe pain and swelling in the affected joint. As the disease develops, bone atrophy in the affected joint becomes evident, although the joint space is maintained throughout the course of the disorder. Increased uptake in the affected joint can be seen with radionuclide bone scan before plain radiography reveals any abnormalities. On MRI scans there are low signal intensity on T1-weighted images and high signal intensity on T2weighted images in the bone marrow of the affected joint, consistent with bone marrow edema.11 In addition, an effusion is usually seen in the joint space. The diagnostic value of CT scan has not been discussed in the literature,4,7 but as shown in this report CT images with numerous spotty defects (without the presence of apparent cortical thinning) are distinct from those of generalized osteoporosis or local osteolytic lesions due to malignant metastasis. They therefore may be helpful for distinguishing RMO from other conditions. The feature that most distinguishes RMO from other disorders is its characteristic migratory behavior and self-limited nature, which can be confirmed by repeated bone scans or MRI examinations,1,16 although it can be confirmed only retrospectively. Hence the diagnosis must be made after careful follow-up and by ruling out more common diseases, such as gout, rheumatoid arthritis, infectious arthritis, primary or metastatic malignancy, tuberculosis, osteomyelitis, disorders of calcium metabolism, and aseptic necrosis.1,7 Our case had, in all respects, a typical clinical presentation and course. The patient was male and in his fifties, with no contributory history. The pain in the right knee started without any particular event, worsened rapidly, and disappeared afterward only to be followed by pain in the right ankle. At the initial presentation, the patient exhibited no specific symptoms; however, slight bone atrophy and effusion in the right knee joint
Discussion Regional migratory osteoporosis is an uncommon, selflimited, clinical entity of unknown etiology.1,2 Possibly due to its rarity and the lack of specific clinical symptoms, the disorder might not be widely recognized. However it is important to distinguish it from other, more aggressive diseases, as spontaneous recovery seems to be the rule for RMO. Regional migratory osteoporosis affects the lower limbs of middle-aged men, usually with no preceding event. Because there is a delay between the onset of the symptoms and the appearance of objective findings on the usual radiographs, early diagnosis may be difficult. Routine laboratory examinations are typically unin-
K. Horiuchi et al.: Regional migratory osteoporosis
led us to investigate further. We then observed bone marrow edema in the femoral condyle and later migration of the lesion. We were thus able to confirm the diagnosis. In our case, we found migration of bone marrow edema within different compartments of the same joint. To our knowledge, this observation has been reported in only five cases in the literature,3,6,10,16,17 although this phenomenon may not be as rare as previously thought.6 Because this condition can be observed only when clinical imaging evaluations (radionuclide bone scans or MRI) are performed rather frequently, the migratory behavior in the same affected joint may simply be overlooked. Nevertheless, this report may be the first to show migration of the lesion both within the same joint and to another joint. The etiology of RMO remains obscure. Several investigators have proposed a hypothesis that prolonged or exaggerated activation of a large number of bone turnover foci caused by a microfracture may contribute to the occurrence of transient osteoporosis.5,8,12 Moreover, recent studies suggesting a possible association of RMO with systemic osteoporosis may support this hypothesis.9,13 Because RMO affects weight-bearing lower limbs and is not seen in young adults, this indeed seems to be a rational explanation. Still, this hypothesis does not fully explain why the disorder mainly affects middle-aged men but not postmenopausal women, in whom there is a more severe and rapid decrease in bone density. It is likely, then, that there are unknown factors contributing to the occurrence of RMO other than an accumulation of microfractures. Recent studies showed the efficacy of intravenous pamidronate for the treatment of both TOH15 and RSD.14 Given that RMO is, in fact, closely related to either or both of these disorders (i.e., it shares a common pathological mechanism in the process of bone resorption), this drug may also have beneficial effects on RMO as well. At any rate, RMO is a self-limited disorder, and each separate lesion usually recovers spontaneously 6–9 months after the onset.1 Hence treatment other than analgesics and protected weightbearing is not necessarily required.
Conclusions We present a case of RMO clearly showing its migratory behavior both within the initially affected joint (right knee) and into the adjacent joint (right ankle). The diagnostic value of MRI, radionuclide bone scan,
181
and plain radiography is well established; and CT scans may be helpful for the differential diagnosis, as shown in this report. With its rare occurrence and unspecific clinical symptoms, RMO may be overlooked or misdiagnosed. With close observation and, most importantly, knowledge of this disease, both clinician and patient can be spared extra trouble. Acknowledgment. We thank Kristie Kelly and Mari Ishii for critically reading the manuscript.
References 1. Banas MP, Kaplan FS, Fallon MD, et al. Regional migratory osteoporosis: a case report and review of the literature. Clin Orthop 1990;250:303–9. 2. Duncan H, Frame B, Frost H, et al. Regional migratory osteoporosis. South Med J 1969;62:41–4. 3. Fertakos RJ, Swayne LC, Colston WC. Three-phase bone imaging in bone marrow edema of the knee. Clin Nucl Med 1995;20:587–90. 4. Froberg PK, Braunstein EM, Buckwalter KA. Osteonecrosis, transient osteoporosis, and transient bone marrow edema: current concepts. Radiol Clin North Am 1996;34:273–91. 5. Frost HM. Perspectives: bone’s mechanical usage windows. Bone Miner 1992;19:257–71. 6. Gaeta M, Mazziotti S, Minutoli F, et al. Migrating transient bone marrow edema syndrome of the knee: MRI findings in a new case. Eur Radiol 2002;12:S40–2. 7. Guerra JJ, Steinberg ME. Distinguishing transient osteoporosis from avascular necrosis of the hip. J Bone Joint Surg Am 1995; 77:616–24. 8. Langloh ND, Hunder GG, Riggs BL, et al. Transient painful osteoporosis of the lower extremities. J Bone Joint Surg Am 1973;55:1188–96. 9. Mavichak V, Murray TM, Hodsman AB, et al. Regional migratory osteoporosis of the lower extremities with vertebral osteoporosis. Bone 1986;7:343–9. 10. Parker RK, Ross GJ, Urso JA. Transient osteoporosis of the knee. Skeletal Radiol 1997;26:306–9. 11. Tannenbaum H, Esdaile J, Rosenthall L. Joint imaging in regional migratory osteoporosis. J Rheumatol 1980;7:237–44. 12. Trevisan C, Ortolani S. Bone loss and recovery in regional migratory osteoporosis. Osteoporos Int 2002;13:901–6. 13. Trevisan C, Ortolani S, Monteleone M, et al. Regional migratory osteoporosis: a pathogenetic hypothesis based on three cases and a review of the literature. Clin Rheumatol 2002;21:418–25. 14. Varenna M, Zucchi F, Ghiringhelli D, et al. Intravenous clodronate in the treatment of reflex sympathetic dystrophy syndrome: a randomized, double blind, placebo controlled study. J Rheumatol 2000;27:1477–83. 15. Varenna M, Zucchi F, Binelli L, et al. Intravenous pamidronate in the treatment of transient osteoporosis of the hip. Bone 2002;31: 96–101. 16. Wambeek N, Munk PL, Lee MJ, et al. Intra-articular regional migratory osteoporosis of the knee. Skeletal Radiol 2000;29:97– 100. 17. Yamasaki S, Masuhara K, Miki H, et al. Three cases of regional migratory osteoporosis. Arch Orthop Trauma Surg 2003;123:439– 41.