An Extra-osseous Intra-articular Osteochondroma of the Elbow

Osteochondromas are among the most common benign osseous tumors, accounting for 20-50% of all benign bone tumors. These tumors often occur before the second decade of life, with a predisposition towards male patients.1De Salvo S. Pavone V. Coco S. Dell’Agli E. Blatti C. Testa G. Benign bone tumors: An overview of what we know today.J Clin Med. 2022; 11https://doi.org/10.3390/jcm11030699Crossref Scopus (0) Google Scholar However, the true incidence is likely underreported due to the potential asymptomatic nature of the tumor, especially in the older subset of affected individuals. Classically, these are surface osseous lesions projecting from the underlying bone and are composed of cortical and medullary components accompanied by a hyaline cartilaginous cap.1De Salvo S. Pavone V. Coco S. Dell’Agli E. Blatti C. Testa G. Benign bone tumors: An overview of what we know today.J Clin Med. 2022; 11https://doi.org/10.3390/jcm11030699Crossref Scopus (0) Google Scholar,11Murphey M.D. Choi J.J. Kransdorf M.J. Flemming D.J. Gannon F.H. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation.Radiographics. 2000; 20: 1407-1434Crossref PubMed Scopus (494) Google Scholar The radiographic features of cortical and medullary continuity with the underlying parent bone is often pathognomonic.11Murphey M.D. Choi J.J. Kransdorf M.J. Flemming D.J. Gannon F.H. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation.Radiographics. 2000; 20: 1407-1434Crossref PubMed Scopus (494) Google ScholarOccurrence sites commonly include the metaphysis and the diametaphysis of long bones including the femur and the tibia, often growing away from the articular surfaces. Symptoms are often derived from secondary fractures, bursa formation and irritation, neurological compromise, joint level involvement and malignant transformation.11Murphey M.D. Choi J.J. Kransdorf M.J. Flemming D.J. Gannon F.H. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation.Radiographics. 2000; 20: 1407-1434Crossref PubMed Scopus (494) Google Scholar The extra-osseous chondromas are separate entities that classically form in the absence of bony attachments. These exists in three variants; synovial chondromatosis, intra-articular chondromas and soft tissue chondromas.3González-Lois C. García-de-la-Torre P. SantosBriz-Terrón A. Vilá J. Manrique-Chico J. Martínez-Tello J. Intracapsular and para-articular chondroma adjacent to large joints: report of three cases and review of the literature.Skeletal Radiol. 2001; 30: 672-676Crossref PubMed Scopus (27) Google Scholar The intra-articular chondroma is an unusual variant that arises from the para-articular connective tissue within joints that possess a sizable capsular space.3González-Lois C. García-de-la-Torre P. SantosBriz-Terrón A. Vilá J. Manrique-Chico J. Martínez-Tello J. Intracapsular and para-articular chondroma adjacent to large joints: report of three cases and review of the literature.Skeletal Radiol. 2001; 30: 672-676Crossref PubMed Scopus (27) Google Scholar The initial growth is a consequence of cartilaginous metaplasia, ultimately leading to ossification, at which point they are termed extra-osseous intra-articular osteochondromas.10Mulcahy H. Hoch B. An extraskeletal para-articular osteochondroma of Hoffa’s fat pad.Radiol Case Rep. 2010; 5: 420https://doi.org/10.2484/rcr.v5i4.420Crossref PubMed Scopus (4) Google ScholarIn this study, we report a case of a 23-year-old male presenting with a symptomatic intraarticular elbow lesion. While radiographic features of the lesion were consistent with an osteochondroma, the extra-osseous characteristics make this presentation unique. To the best of the author’s knowledge, this is the first report of an entirely extra-osseous, intra-articular osteochondroma arising in the olecranon fossa.Case ReportA previously healthy, 23-year-old male patient was referred to our tertiary orthopedic center complaining of an insidious onset of dull pain in the right elbow associated with progressive range of motion limitation for the past three months. Initial analgesics were attempted by the patient prior to presenting to healthcare services. The patient noticed a hard swelling overlying the posterior aspect of the elbow joint. There was no history of trauma, constitutional symptoms or infection.Physical examination revealed a hard, mildly tender mass deep to the posterior elbow joint. Range of motion was restricted by 5 to 10 degrees at the extremes of flexion and extension. There were no abnormalities relating to skin condition, temperature and deformities. Neurovascular examination was unremarkable. A general whole-body examination was unremarkable for any pathology.Hematological and biochemical investigations performed did not reveal any abnormalities. Plain radiographs of the right elbow revealed an osseous mass located in the olecranon fossa with features of a sclerotic and calcified cortical margin. (Fig.1) The rest of the ipsilateral limb was otherwise normal. A non-enhanced magnetic resonance image (MRI) showed a well-defined intra-articular nodule (2.8 x 2.6 x 1.7 cm) in the right elbow's posterior joint space, with internal mineralization areas. (Fig. 2,3)Figure 2Axial and sagittal magnetic resonance imaging (MRI) sections of the right elbow showing an intra-articular osseous massView Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Axial and sagittal magnetic resonance imaging (MRI) sections of the right elbow showing an intra-articular osseous massView Large Image Figure ViewerDownload Hi-res image Download (PPT)Next, a computed tomography (CT) guided core needle biopsy was performed. Samples were subsequently analyzed by a clinical histopathologist. The sections showed two cores of hyaline cartilage, one of which was focally covered with synovial lining. In addition, the hyaline cartilage showed a focal increase in cellularity, with few cells showing mild to moderate nuclear atypia. The histopathological differential diagnosis of well-differentiated cartilage on core biopsy included several bone lesions, such as enchondroma, atypical cartilaginous lesions/well-differentiated chondrosarcoma, cartilaginous cap osteochondroma, and synovial chondromatosis. A definite histopathological diagnosis of osteochondroma could not be made at this point due to the unusual location, atypical radiological features and inability to appreciate the characteristic architectural features on limited biopsy material.After obtaining consent from the patient, the patient underwent surgical exploration through a direct posterior elbow approach. The lesion was intra-articular, situated in the olecranon fossa, and extra-osseous. (Fig. 4) It had no continuity with the underlying bone. Grossly, the external surface was knobby and bluish-white, and was consistent with features of an osteochondroma. (Fig. 5) Marginal excision of the lesion was performed, and intra-operative fluoroscopic images confirmed adequate resection. Intra-operatively following excision of the lesion, full passive range of elbow flexion and extension was achieved. No elbow immobilization was required, and the elbow and forearm's active range of motion exercises were encouraged immediately postoperatively.Figure 4Operative findings: posterior right elbow approach revealing a solid mass consisting of osseocartilaginous nodules situated in the olecranon fossaView Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 5Gross specimen of the osteochondroma after surgical removal.View Large Image Figure ViewerDownload Hi-res image Download (PPT)The sample was subsequently sent for a final histopathological assessment. It consisted of a lobulated bony outgrowth with a smooth outer surface measuring 4.0 x 2.6 x 1.5 cm. (Fig. 6) The cut surface revealed a cartilaginous cap that is less than 2 cm in maximum thickness with an underlying broad base. (Fig. 7) Microscopic sections confirmed the presence of a cartilaginous cap composed of well-differentiated hyaline cartilage and covered by perichondrium. The cartilage displayed a lobular arrangement of chondrocytes with enchondral ossification reminiscent of an epiphyseal plate. No significant nuclear atypia or mitosis was seen and there was no evidence of permeation of preexisting bone histologically, ruling out well-differentiated chondrosarcoma. Fatty marrow elements were present within the bony stalk. The overall pathological features were those of a sessile osteochondroma.Figure 6Macroscopic appearance of the specimen: Bosselated outer surface covered by smooth perichondriumView Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 7Macroscopic appearance of the specimen: Cut surface showed a cartilaginous cap not exceeding 2cm in thickness (arrow) and a stalk containing marrow elements.View Large Image Figure ViewerDownload Hi-res image Download (PPT)The patient had an uneventful postoperative phase and performed gradual full range of motion exercises of the elbow joint. The patient regained full range of motion and symptom resolution.DiscussionOsteochondromas are the most common benign bone tumors occurring around the growth plates of long bones, especially in the skeletally immature population, and tend to extend into the diaphysis.5Jang S.-H. Song H.-E. Arthroscopic excision of intra-articular osteochondroma of the elbow: A case report.Clin Shoulder Elb. 2016; 19: 172-175https://doi.org/10.5397/cise.2016.19.3.172Crossref Google Scholar Most common locations include the distal femur, the proximal tibia, and the humerus. Thus, an intra-articular osteochondroma in an adult is quite rare. In 1891, Virchow et al hypothesized that an osteochondroma is derived from aberrant cartilaginous tissue arising from the physis that separates during growth and gives rise to a separate area of bone formation through endochondral ossification.14Virchow R. Ueber multiple Exostosen, mit Vorlegung Von Praparten.. Berl. Klin. Wochenschr. 1891; 28: 1082Google Scholar This hypothesis was further supported by a histopathologic study conducted by Milgram.7Milgram J.W. The origins of osteochondromas and enchondromas. A histopathologic study.Clin Orthop Relat Res. 1983 Apr; 174: 264-284Crossref PubMed Google ScholarWhile extra-articular osteochondromas are usually asymptomatic, intra-articular variants cause pain and limitations in the range of motion of the affected joint. Jaffe et al first described intra-articular osteochondromas in 1958 as lesions that occur in the joint capsule or the soft tissue adjacent to the affected joint and thus termed the lesions para-articular chondromas or intracapsular chondromas.4Jaffe H. Tumors and tumorous conditions of the bones and joints. Philadelphia: Lea and Febiger. 1958;558–67.Google Scholar Eventually, the term para-articular osteochondromas was established to discriminate the latter from synovial chondromatosis.12Rizzello G. Franceschi F. Meloni M.C. Cristi E. Barnaba S.A. Rabitti C. et al.Para-articular osteochondroma of the knee.Arthroscopy. 2007; 23 (910.e1-4)https://doi.org/10.1016/j.arthro.2006.05.030Abstract Full Text Full Text PDF Scopus (18) Google Scholar Extra-skeletal osteochondromas are believed to originate from the differentiation of mesenchymal cells of the soft tissues.6Malhotra K. Nunn T. Chandramohan M. Shanker J. Metatarsal stress fractures secondary to soft-tissue osteochondroma in the foot: case report and literature review.Foot Ankle Surg. 2011; 17: e51-e54https://doi.org/10.1016/j.fas.2011.05.003Crossref PubMed Scopus (7) Google Scholar Further, intra-articular osteochondromas are usually described as tumors composed of a single mass with multiple osteochondral nodules in which marginal resection or conventional surgical excision is the definitive treatment of choice.12Rizzello G. Franceschi F. Meloni M.C. Cristi E. Barnaba S.A. Rabitti C. et al.Para-articular osteochondroma of the knee.Arthroscopy. 2007; 23 (910.e1-4)https://doi.org/10.1016/j.arthro.2006.05.030Abstract Full Text Full Text PDF Scopus (18) Google Scholar,9Mosher Jr., J.F. Kettelkamp D.B. Campbell C.J. Intracapsular or para-articular chondroma. A report of three cases.J Bone Joint Surg Am. 1966; 48: 1561-1569Crossref PubMed Scopus (33) Google Scholar Thus highlighting the importance of appropriate diagnoses to guide management.Several cases of intra-articular osteochondromas of the elbow joint were reported in the literature. Morin et al reported a case of a 14-year-old girl who presented with a progressive contracture of the left elbow joint. Although initially diagnosed as a post-traumatic flexion contracture, an elbow's computed tomography (CT) showed increased bone density arising from the distal humerus with an extension into the coronoid and olecranon fossa. The diagnosis of intra-articular osteochondroma was confirmed by histological examination.8Morin B. Pelletier A. Cisa J. Marton D. Intraarticular osteochondroma of the elbow.J Shoulder Elbow Surg. 1994; 3: 270-272Abstract Full Text PDF PubMed Google ScholarDittrich et al also reported a case of a 33-year-old gentleman who presented with pain and loss of motion of the right elbow. Imaging revealed small shadows within the proximal radioulnar joint space. Intra-operatively, the capsule was incised and revealed three extra-skeletal bony structures attached by fine cartilage strands and bone. Although extra-osseous, it was situated in the proximal radioulnar joint rather than the olecranon fossa.2Dittrich R.J. Osteochondromatosis of the elbow.Am J Surg. 1946; 72: 125-127Abstract Full Text PDF PubMed Google Scholar Shariatzadeh et al similarly reported a case of a 33-year-old woman who presented with right elbow limitation of motion and pain for three years. Radiographical studies showed an osseous mass in the anterior aspect of the distal humerus with a calcified cortical margin. Intra-operatively they found a completely intra-articular lobulate white mass with a chondral covering consistent with the typical cap of an osteochondroma. In contrast to our case, which was completely extra-osseous, this lesion was continuous with the capitellum and the trochlea.13Shariatzadeh H. Jafari D. Taheri H. Jamshidi K. Pahlevansabagh A. Intra-articular osteochondroma of the elbow: a case report.J Shoulder Elbow Surg. 2010; 19: e1-4https://doi.org/10.1016/j.jse.2009.09.013Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar While there have been reports of arthroscopic excision being performed, open surgical exploration and careful excision remains the gold standard of treatment.5Jang S.-H. Song H.-E. Arthroscopic excision of intra-articular osteochondroma of the elbow: A case report.Clin Shoulder Elb. 2016; 19: 172-175https://doi.org/10.5397/cise.2016.19.3.172Crossref Google ScholarConclusionIn this study, we describe the first case of an extra-osseous, intra-articular osteochondroma of the elbow joint situated in the olecranon fossa. Appropriate workup abiding by standard principles and subsequent surgical excision result in excellent results and symptom resolution. We advocate for careful diagnoses and a high index of suspicion in these exceedingly rare tumors in order to avoid overtreatment. Osteochondromas are among the most common benign osseous tumors, accounting for 20-50% of all benign bone tumors. These tumors often occur before the second decade of life, with a predisposition towards male patients.1De Salvo S. Pavone V. Coco S. Dell’Agli E. Blatti C. Testa G. Benign bone tumors: An overview of what we know today.J Clin Med. 2022; 11https://doi.org/10.3390/jcm11030699Crossref Scopus (0) Google Scholar However, the true incidence is likely underreported due to the potential asymptomatic nature of the tumor, especially in the older subset of affected individuals. Classically, these are surface osseous lesions projecting from the underlying bone and are composed of cortical and medullary components accompanied by a hyaline cartilaginous cap.1De Salvo S. Pavone V. Coco S. Dell’Agli E. Blatti C. Testa G. Benign bone tumors: An overview of what we know today.J Clin Med. 2022; 11https://doi.org/10.3390/jcm11030699Crossref Scopus (0) Google Scholar,11Murphey M.D. Choi J.J. Kransdorf M.J. Flemming D.J. Gannon F.H. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation.Radiographics. 2000; 20: 1407-1434Crossref PubMed Scopus (494) Google Scholar The radiographic features of cortical and medullary continuity with the underlying parent bone is often pathognomonic.11Murphey M.D. Choi J.J. Kransdorf M.J. Flemming D.J. Gannon F.H. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation.Radiographics. 2000; 20: 1407-1434Crossref PubMed Scopus (494) Google Scholar Occurrence sites commonly include the metaphysis and the diametaphysis of long bones including the femur and the tibia, often growing away from the articular surfaces. Symptoms are often derived from secondary fractures, bursa formation and irritation, neurological compromise, joint level involvement and malignant transformation.11Murphey M.D. Choi J.J. Kransdorf M.J. Flemming D.J. Gannon F.H. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation.Radiographics. 2000; 20: 1407-1434Crossref PubMed Scopus (494) Google Scholar The extra-osseous chondromas are separate entities that classically form in the absence of bony attachments. These exists in three variants; synovial chondromatosis, intra-articular chondromas and soft tissue chondromas.3González-Lois C. García-de-la-Torre P. SantosBriz-Terrón A. Vilá J. Manrique-Chico J. Martínez-Tello J. Intracapsular and para-articular chondroma adjacent to large joints: report of three cases and review of the literature.Skeletal Radiol. 2001; 30: 672-676Crossref PubMed Scopus (27) Google Scholar The intra-articular chondroma is an unusual variant that arises from the para-articular connective tissue within joints that possess a sizable capsular space.3González-Lois C. García-de-la-Torre P. SantosBriz-Terrón A. Vilá J. Manrique-Chico J. Martínez-Tello J. Intracapsular and para-articular chondroma adjacent to large joints: report of three cases and review of the literature.Skeletal Radiol. 2001; 30: 672-676Crossref PubMed Scopus (27) Google Scholar The initial growth is a consequence of cartilaginous metaplasia, ultimately leading to ossification, at which point they are termed extra-osseous intra-articular osteochondromas.10Mulcahy H. Hoch B. An extraskeletal para-articular osteochondroma of Hoffa’s fat pad.Radiol Case Rep. 2010; 5: 420https://doi.org/10.2484/rcr.v5i4.420Crossref PubMed Scopus (4) Google Scholar In this study, we report a case of a 23-year-old male presenting with a symptomatic intraarticular elbow lesion. While radiographic features of the lesion were consistent with an osteochondroma, the extra-osseous characteristics make this presentation unique. To the best of the author’s knowledge, this is the first report of an entirely extra-osseous, intra-articular osteochondroma arising in the olecranon fossa. Case ReportA previously healthy, 23-year-old male patient was referred to our tertiary orthopedic center complaining of an insidious onset of dull pain in the right elbow associated with progressive range of motion limitation for the past three months. Initial analgesics were attempted by the patient prior to presenting to healthcare services. The patient noticed a hard swelling overlying the posterior aspect of the elbow joint. There was no history of trauma, constitutional symptoms or infection.Physical examination revealed a hard, mildly tender mass deep to the posterior elbow joint. Range of motion was restricted by 5 to 10 degrees at the extremes of flexion and extension. There were no abnormalities relating to skin condition, temperature and deformities. Neurovascular examination was unremarkable. A general whole-body examination was unremarkable for any pathology.Hematological and biochemical investigations performed did not reveal any abnormalities. Plain radiographs of the right elbow revealed an osseous mass located in the olecranon fossa with features of a sclerotic and calcified cortical margin. (Fig.1) The rest of the ipsilateral limb was otherwise normal. A non-enhanced magnetic resonance image (MRI) showed a well-defined intra-articular nodule (2.8 x 2.6 x 1.7 cm) in the right elbow's posterior joint space, with internal mineralization areas. (Fig. 2,3)Figure 3Axial and sagittal magnetic resonance imaging (MRI) sections of the right elbow showing an intra-articular osseous massView Large Image Figure ViewerDownload Hi-res image Download (PPT)Next, a computed tomography (CT) guided core needle biopsy was performed. Samples were subsequently analyzed by a clinical histopathologist. The sections showed two cores of hyaline cartilage, one of which was focally covered with synovial lining. In addition, the hyaline cartilage showed a focal increase in cellularity, with few cells showing mild to moderate nuclear atypia. The histopathological differential diagnosis of well-differentiated cartilage on core biopsy included several bone lesions, such as enchondroma, atypical cartilaginous lesions/well-differentiated chondrosarcoma, cartilaginous cap osteochondroma, and synovial chondromatosis. A definite histopathological diagnosis of osteochondroma could not be made at this point due to the unusual location, atypical radiological features and inability to appreciate the characteristic architectural features on limited biopsy material.After obtaining consent from the patient, the patient underwent surgical exploration through a direct posterior elbow approach. The lesion was intra-articular, situated in the olecranon fossa, and extra-osseous. (Fig. 4) It had no continuity with the underlying bone. Grossly, the external surface was knobby and bluish-white, and was consistent with features of an osteochondroma. (Fig. 5) Marginal excision of the lesion was performed, and intra-operative fluoroscopic images confirmed adequate resection. Intra-operatively following excision of the lesion, full passive range of elbow flexion and extension was achieved. No elbow immobilization was required, and the elbow and forearm's active range of motion exercises were encouraged immediately postoperatively.Figure 4Operative findings: posterior right elbow approach revealing a solid mass consisting of osseocartilaginous nodules situated in the olecranon fossaView Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 5Gross specimen of the osteochondroma after surgical removal.View Large Image Figure ViewerDownload Hi-res image Download (PPT)The sample was subsequently sent for a final histopathological assessment. It consisted of a lobulated bony outgrowth with a smooth outer surface measuring 4.0 x 2.6 x 1.5 cm. (Fig. 6) The cut surface revealed a cartilaginous cap that is less than 2 cm in maximum thickness with an underlying broad base. (Fig. 7) Microscopic sections confirmed the presence of a cartilaginous cap composed of well-differentiated hyaline cartilage and covered by perichondrium. The cartilage displayed a lobular arrangement of chondrocytes with enchondral ossification reminiscent of an epiphyseal plate. No significant nuclear atypia or mitosis was seen and there was no evidence of permeation of preexisting bone histologically, ruling out well-differentiated chondrosarcoma. Fatty marrow elements were present within the bony stalk. The overall pathological features were those of a sessile osteochondroma.Figure 6Macroscopic appearance of the specimen: Bosselated outer surface covered by smooth perichondriumView Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 7Macroscopic appearance of the specimen: Cut surface showed a cartilaginous cap not exceeding 2cm in thickness (arrow) and a stalk containing marrow elements.View Large Image Figure ViewerDownload Hi-res image Download (PPT)The patient had an uneventful postoperative phase and performed gradual full range of motion exercises of the elbow joint. The patient regained full range of motion and symptom resolution. A previously healthy, 23-year-old male patient was referred to our tertiary orthopedic center complaining of an insidious onset of dull pain in the right elbow associated with progressive range of motion limitation for the past three months. Initial analgesics were attempted by the patient prior to presenting to healthcare services. The patient noticed a hard swelling overlying the posterior aspect of the elbow joint. There was no history of trauma, constitutional symptoms or infection. Physical examination revealed a hard, mildly tender mass deep to the posterior elbow joint. Range of motion was restricted by 5 to 10 degrees at the extremes of flexion and extension. There were no abnormalities relating to skin condition, temperature and deformities. Neurovascular examination was unremarkable. A general whole-body examination was unremarkable for any pathology. Hematological and biochemical investigations performed did not reveal any abnormalities. Plain radiographs of the right elbow revealed an osseous mass located in the olecranon fossa with features of a sclerotic and calcified cortical margin. (Fig.1) The rest of the ipsilateral limb was otherwise normal. A non-enhanced magnetic resonance image (MRI) showed a well-defined intra-articular nodule (2.8 x 2.6 x 1.7 cm) in the right elbow's posterior joint space, with internal mineralization areas. (Fig. 2,3) Next, a computed tomography (CT) guided core needle biopsy was performed. Samples were subsequently analyzed by a clinical histopathologist. The sections showed two cores of hyaline cartilage, one of which was focally covered with synovial lining. In addition, the hyaline cartilage showed a focal increase in cellularity, with few cells showing mild to moderate nuclear atypia. The histopathological differential diagnosis of well-differentiated cartilage on core biopsy included several bone lesions, such as enchondroma, atypical cartilaginous lesions/well-differentiated chondrosarcoma, cartilaginous cap osteochondroma, and synovial chondromatosis. A definite histopathological diagnosis of osteochondroma could not be made at this point due to the unusual location, atypical radiological features and inability to appreciate the characteristic architectural features on limited biopsy material. After obtaining consent from the patient, the patient underwent surgical exploration through a direct posterior elbow approach. The lesion was intra-articular, situated in the olecranon fossa, and extra-osseous. (Fig. 4) It had no continuity with the underlying bone. Grossly, the external surface was knobby and bluish-white, and was consistent with features of an osteochondroma. (Fig. 5) Marginal excision of the lesion was performed, and intra-operative fluoroscopic images confirmed adequate resection. Intra-operatively following excision of the lesion, full passive range of elbow flexion and extension was achieved. No elbow immobilization was required, and the elbow and forearm's active range of motion exercises were encouraged immediately postoperatively. The sample was subsequently sent for a final histopathological assessment. It consisted of a lobulated bony outgrowth with a smooth outer surface measuring 4.0 x 2.6 x 1.5 cm. (Fig. 6) The cut surface revealed a cartilaginous cap that is less than 2 cm in maximum thickness with an underlying broad base. (Fig. 7) Microscopic sections confirmed the presence of a cartilaginous cap composed of well-differentiated hyaline cartilage and covered by perichondrium. The cartilage displayed a lobular arrangement of chondrocytes with enchondral ossification reminiscent of an epiphyseal plate. No significant nuclear atypia or mitosis was seen and there was no evidence of permeation of preexisting bone histologically, ruling out well-differentiated chondrosarcoma. Fatty marrow elements were present within the bony stalk. The overall pathological features were those of a sessile osteochondroma. The patient had an uneventful postoperative phase and performed gradual full range of motion exercises of the elbow joint. The patient regained full range of motion and symptom resolution. DiscussionOsteochondromas are the most common benign bone tumors occurring around the growth plates of long bones, especially in the skeletally immature population, and tend to extend into the diaphysis.5Jang S.-H. Song H.-E. Arthroscopic excision of intra-articular osteochondroma of the elbow: A case report.Clin Shoulder Elb. 2016; 19: 172-175https://doi.org/10.5397/cise.2016.19.3.172Crossref Google Scholar Most common locations include the distal femur, the proximal tibia, and the humerus. Thus, an intra-articular osteochondroma in an adult is quite rare. In 1891, Virchow et al hypothesized that an osteochondroma is derived from aberrant cartilaginous tissue arising from the physis that separates during growth and gives rise to a separate area of bone formation through endochondral ossification.14Virchow R. Ueber multiple Exostosen, mit Vorlegung Von Praparten.. Berl. Klin. Wochenschr. 1891; 28: 1082Google Scholar This hypothesis was further supported by a histopathologic study conducted by Milgram.7Milgram J.W. The origins of osteochondromas and enchondromas. A histopathologic study.Clin Orthop Relat Res. 1983 Apr; 174: 264-284Crossref PubMed Google ScholarWhile extra-articular osteochondromas are usually asymptomatic, intra-articular variants cause pain and limitations in the range of motion of the affected joint. Jaffe et al first described intra-articular osteochondromas in 1958 as lesions that occur in the joint capsule or the soft tissue adjacent to the affected joint and thus termed the lesions para-articular chondromas or intracapsular chondromas.4Jaffe H. Tumors and tumorous conditions of the bones and joints. Philadelphia: Lea and Febiger. 1958;558–67.Google Scholar Eventually, the term para-articular osteochondromas was established to discriminate the latter from synovial chondromatosis.12Rizzello G. Franceschi F. Meloni M.C. Cristi E. Barnaba S.A. Rabitti C. et al.Para-articular osteochondroma of the knee.Arthroscopy. 2007; 23 (910.e1-4)https://doi.org/10.1016/j.arthro.2006.05.030Abstract Full Text Full Text PDF Scopus (18) Google Scholar Extra-skeletal osteochondromas are believed to originate from the differentiation of mesenchymal cells of the soft tissues.6Malhotra K. Nunn T. Chandramohan M. Shanker J. Metatarsal stress fractures secondary to soft-tissue osteochondroma in the foot: case report and literature review.Foot Ankle Surg. 2011; 17: e51-e54https://doi.org/10.1016/j.fas.2011.05.003Crossref PubMed Scopus (7) Google Scholar Further, intra-articular osteochondromas are usually described as tumors composed of a single mass with multiple osteochondral nodules in which marginal resection or conventional surgical excision is the definitive treatment of choice.12Rizzello G. Franceschi F. Meloni M.C. Cristi E. Barnaba S.A. Rabitti C. et al.Para-articular osteochondroma of the knee.Arthroscopy. 2007; 23 (910.e1-4)https://doi.org/10.1016/j.arthro.2006.05.030Abstract Full Text Full Text PDF Scopus (18) Google Scholar,9Mosher Jr., J.F. Kettelkamp D.B. Campbell C.J. Intracapsular or para-articular chondroma. A report of three cases.J Bone Joint Surg Am. 1966; 48: 1561-1569Crossref PubMed Scopus (33) Google Scholar Thus highlighting the importance of appropriate diagnoses to guide management.Several cases of intra-articular osteochondromas of the elbow joint were reported in the literature. Morin et al reported a case of a 14-year-old girl who presented with a progressive contracture of the left elbow joint. Although initially diagnosed as a post-traumatic flexion contracture, an elbow's computed tomography (CT) showed increased bone density arising from the distal humerus with an extension into the coronoid and olecranon fossa. The diagnosis of intra-articular osteochondroma was confirmed by histological examination.8Morin B. Pelletier A. Cisa J. Marton D. Intraarticular osteochondroma of the elbow.J Shoulder Elbow Surg. 1994; 3: 270-272Abstract Full Text PDF PubMed Google ScholarDittrich et al also reported a case of a 33-year-old gentleman who presented with pain and loss of motion of the right elbow. Imaging revealed small shadows within the proximal radioulnar joint space. Intra-operatively, the capsule was incised and revealed three extra-skeletal bony structures attached by fine cartilage strands and bone. Although extra-osseous, it was situated in the proximal radioulnar joint rather than the olecranon fossa.2Dittrich R.J. Osteochondromatosis of the elbow.Am J Surg. 1946; 72: 125-127Abstract Full Text PDF PubMed Google Scholar Shariatzadeh et al similarly reported a case of a 33-year-old woman who presented with right elbow limitation of motion and pain for three years. Radiographical studies showed an osseous mass in the anterior aspect of the distal humerus with a calcified cortical margin. Intra-operatively they found a completely intra-articular lobulate white mass with a chondral covering consistent with the typical cap of an osteochondroma. In contrast to our case, which was completely extra-osseous, this lesion was continuous with the capitellum and the trochlea.13Shariatzadeh H. Jafari D. Taheri H. Jamshidi K. Pahlevansabagh A. Intra-articular osteochondroma of the elbow: a case report.J Shoulder Elbow Surg. 2010; 19: e1-4https://doi.org/10.1016/j.jse.2009.09.013Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar While there have been reports of arthroscopic excision being performed, open surgical exploration and careful excision remains the gold standard of treatment.5Jang S.-H. Song H.-E. Arthroscopic excision of intra-articular osteochondroma of the elbow: A case report.Clin Shoulder Elb. 2016; 19: 172-175https://doi.org/10.5397/cise.2016.19.3.172Crossref Google Scholar Osteochondromas are the most common benign bone tumors occurring around the growth plates of long bones, especially in the skeletally immature population, and tend to extend into the diaphysis.5Jang S.-H. Song H.-E. Arthroscopic excision of intra-articular osteochondroma of the elbow: A case report.Clin Shoulder Elb. 2016; 19: 172-175https://doi.org/10.5397/cise.2016.19.3.172Crossref Google Scholar Most common locations include the distal femur, the proximal tibia, and the humerus. Thus, an intra-articular osteochondroma in an adult is quite rare. In 1891, Virchow et al hypothesized that an osteochondroma is derived from aberrant cartilaginous tissue arising from the physis that separates during growth and gives rise to a separate area of bone formation through endochondral ossification.14Virchow R. Ueber multiple Exostosen, mit Vorlegung Von Praparten.. Berl. Klin. Wochenschr. 1891; 28: 1082Google Scholar This hypothesis was further supported by a histopathologic study conducted by Milgram.7Milgram J.W. The origins of osteochondromas and enchondromas. A histopathologic study.Clin Orthop Relat Res. 1983 Apr; 174: 264-284Crossref PubMed Google Scholar While extra-articular osteochondromas are usually asymptomatic, intra-articular variants cause pain and limitations in the range of motion of the affected joint. Jaffe et al first described intra-articular osteochondromas in 1958 as lesions that occur in the joint capsule or the soft tissue adjacent to the affected joint and thus termed the lesions para-articular chondromas or intracapsular chondromas.4Jaffe H. Tumors and tumorous conditions of the bones and joints. Philadelphia: Lea and Febiger. 1958;558–67.Google Scholar Eventually, the term para-articular osteochondromas was established to discriminate the latter from synovial chondromatosis.12Rizzello G. Franceschi F. Meloni M.C. Cristi E. Barnaba S.A. Rabitti C. et al.Para-articular osteochondroma of the knee.Arthroscopy. 2007; 23 (910.e1-4)https://doi.org/10.1016/j.arthro.2006.05.030Abstract Full Text Full Text PDF Scopus (18) Google Scholar Extra-skeletal osteochondromas are believed to originate from the differentiation of mesenchymal cells of the soft tissues.6Malhotra K. Nunn T. Chandramohan M. Shanker J. Metatarsal stress fractures secondary to soft-tissue osteochondroma in the foot: case report and literature review.Foot Ankle Surg. 2011; 17: e51-e54https://doi.org/10.1016/j.fas.2011.05.003Crossref PubMed Scopus (7) Google Scholar Further, intra-articular osteochondromas are usually described as tumors composed of a single mass with multiple osteochondral nodules in which marginal resection or conventional surgical excision is the definitive treatment of choice.12Rizzello G. Franceschi F. Meloni M.C. Cristi E. Barnaba S.A. Rabitti C. et al.Para-articular osteochondroma of the knee.Arthroscopy. 2007; 23 (910.e1-4)https://doi.org/10.1016/j.arthro.2006.05.030Abstract Full Text Full Text PDF Scopus (18) Google Scholar,9Mosher Jr., J.F. Kettelkamp D.B. Campbell C.J. Intracapsular or para-articular chondroma. A report of three cases.J Bone Joint Surg Am. 1966; 48: 1561-1569Crossref PubMed Scopus (33) Google Scholar Thus highlighting the importance of appropriate diagnoses to guide management. Several cases of intra-articular osteochondromas of the elbow joint were reported in the literature. Morin et al reported a case of a 14-year-old girl who presented with a progressive contracture of the left elbow joint. Although initially diagnosed as a post-traumatic flexion contracture, an elbow's computed tomography (CT) showed increased bone density arising from the distal humerus with an extension into the coronoid and olecranon fossa. The diagnosis of intra-articular osteochondroma was confirmed by histological examination.8Morin B. Pelletier A. Cisa J. Marton D. Intraarticular osteochondroma of the elbow.J Shoulder Elbow Surg. 1994; 3: 270-272Abstract Full Text PDF PubMed Google Scholar Dittrich et al also reported a case of a 33-year-old gentleman who presented with pain and loss of motion of the right elbow. Imaging revealed small shadows within the proximal radioulnar joint space. Intra-operatively, the capsule was incised and revealed three extra-skeletal bony structures attached by fine cartilage strands and bone. Although extra-osseous, it was situated in the proximal radioulnar joint rather than the olecranon fossa.2Dittrich R.J. Osteochondromatosis of the elbow.Am J Surg. 1946; 72: 125-127Abstract Full Text PDF PubMed Google Scholar Shariatzadeh et al similarly reported a case of a 33-year-old woman who presented with right elbow limitation of motion and pain for three years. Radiographical studies showed an osseous mass in the anterior aspect of the distal humerus with a calcified cortical margin. Intra-operatively they found a completely intra-articular lobulate white mass with a chondral covering consistent with the typical cap of an osteochondroma. In contrast to our case, which was completely extra-osseous, this lesion was continuous with the capitellum and the trochlea.13Shariatzadeh H. Jafari D. Taheri H. Jamshidi K. Pahlevansabagh A. Intra-articular osteochondroma of the elbow: a case report.J Shoulder Elbow Surg. 2010; 19: e1-4https://doi.org/10.1016/j.jse.2009.09.013Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar While there have been reports of arthroscopic excision being performed, open surgical exploration and careful excision remains the gold standard of treatment.5Jang S.-H. Song H.-E. Arthroscopic excision of intra-articular osteochondroma of the elbow: A case report.Clin Shoulder Elb. 2016; 19: 172-175https://doi.org/10.5397/cise.2016.19.3.172Crossref Google Scholar ConclusionIn this study, we describe the first case of an extra-osseous, intra-articular osteochondroma of the elbow joint situated in the olecranon fossa. Appropriate workup abiding by standard principles and subsequent surgical excision result in excellent results and symptom resolution. We advocate for careful diagnoses and a high index of suspicion in these exceedingly rare tumors in order to avoid overtreatment. In this study, we describe the first case of an extra-osseous, intra-articular osteochondroma of the elbow joint situated in the olecranon fossa. Appropriate workup abiding by standard principles and subsequent surgical excision result in excellent results and symptom resolution. We advocate for careful diagnoses and a high index of suspicion in these exceedingly rare tumors in order to avoid overtreatment.