we report an unusual case of partial anterior cruciate ligament ( acl ) tear secondary to a glass foreign body in an adolescent knee joint . a 13-year - old boy presented with pain , swelling and deformity of the left knee since 4 days . the glass foreign body remained in the subcutaneous tissue for few days and later migrated into the knee joint . arthroscopy revealed partial tear in the acl at the femoral attachment with about 10 - 20 % of fibres being involved . arthroscopic removal of foreign bodies from the knee is a very simple procedure and has the advantages of avoiding large incision , shorter stay in the hospital , faster recovery and reduced infection rates . glass foreign bodies were previously implicated in cartilage damage and meniscal injuries but a foreign body resulting in acl tear has not been reported in literature . various types of foreign bodies have been removed from the knee joint such as needle , glass , lead of pencil , mercury thermometer , blades , thorn , bullet , screws and sometimes arthroscopic instruments like tip of shaver [ 1 - 6 ] . we report an unusual case of partial anterior cruciate ligament ( acl ) tear secondary to a glass foreign body in an adolescent knee joint . a 13-year - old boy presented with pain , swelling , deformity and inability to bear weight . he gave a history of a fall on glass pieces while playing 9 days ago . he was taken to a nearby hospital where x - rays of the knee were done ; no abnormality was noticed and was prescribed analgesics . symptoms worsened after 2 days when he developed deformity of knee and inability to bear weight on the affected side . he was then taken to a different hospital where he was diagnosed to have a foreign body in his knee and referred to our institution for further management . on examination , the left knee was in 30 degrees flexion , supra - patellar fullness and mild effusion was noted . an oblique skin laceration of 1x1 cm was noted lateral to the patella ( fig . 1 ) . there was no active discharge from the wound or local raise of temperature . boy was unable to move his knee due to pain and did not allow us to examine him thoroughly . clinical photograph of the left knee flexion deformity ( a ) and insert demonstrating an oblique laceration of 1x1 cm just lateral to the patella(b ) . antero - posterior and lateral radiographs of the knee done 5 days prior to admission showed a radio - opaque shadow measuring about 1x1 cm in the supero - lateral quadrant of the knee , residing in the superficial planes , perhaps in the subcutaneous tissues ( fig . this explains the child not having symptoms for the first 4 days . at the time of presentation to our out - patient department freshly taken radiographs revealed radio - opaque shadow in the inter - condylar region of the knee in front of the tibial attachment of the anterior cruciate ligament ( acl ) resembling an avulsion of the acl from the tibial plateau ( fig . mri scan of the knee was not considered as the history and follow - up events suggested a foreign body in the knee and this would not have changed our management plan . radiographs of the knee joint taken a few days prior to admission showing radio opaque shadow measuring about 1x1 cm in the supero - lateral quadrant of the knee , in the superficial planes . antero - posterior , lateral and skyline x - ray views of the left knee joint demonstrating radio opaque shadow in the region of the tibial attachment of the anterior cruciate ligament ( acl ) , mimicking an avulsion fracture of the tibial spine . under general anaesthesia , the knee deformity was spontaneously corrected suggesting that it may have been due to muscle spasm . 4 ) lying in the inter - condylar notch in the space between the acl and the lateral surface of the medial femoral condyle . 5 ) arthroscopically with the help of a small artery forceps by increasing the size of medial portal . the synovium in the supra - patellar pouch , medial and lateral gutter was hyperaemic . there was no obvious damage to menisci or the articular surfaces of the femoral or tibial condyles except for some abrasions ( video 1 ) . arthroscopic image of the glass piece in the knee joint which was found lying in the inter - condylar notch in the space between the acl and the lateral surface of the medial femoral condyle . arthroscopically extracted glass foreign body with sharp edges measuring 1 cm x 1 cm . a partial tear in the acl at the femoral attachment with 10 - 20 % of fibres being involved was noted probably due to the sharp edges of the glass piece ( fig . there was a small tear of 1x1 cm in the lateral retinaculum below the skin laceration , which was repaired . arthroscopic view of partial tear in the acl at the femoral attachment with about 10 - 20 % of fibres being involved . post - operatively , the boy was allowed full weight - bearing and knee mobilisation exercises were started . no deformity was noted post - operatively . at the end of 1 year of follow - up , many of the times , penetrating wounds ( i.e. , after an accidental fall , road traffic accidents ) remain the major cause of foreign body in the knee . remaining injuries are sustained by missiles shot by machinery for civilian use ( e.g. , power - gun nails , needles , staples ) or by weapons . rarely , the cause can be iatrogenic ( e.g. arthroscopic instruments for e.g. tip of shaver blades , staples , suture materials , anchors , broken screws used for graft fixation ) [ 2 , 3 ] . metal , glass pieces , and lead objects are radio - opaque and can be identified on x - rays . objects like thorns , stones , suture material , and bio - absorbable screws are radiolucent and can only be detected by an ultrasound or an mri . the presence of a local scar can give a clue to the underlying pathology , as in our case a glass piece had entered from the antero - lateral aspect of the knee joint . whereas in some cases the cause of uncertain knee complaints especially in children can be due to foreign bodies which penetrated unnoticed into the joint cavity . earlier the better , as the amount of intra - articular damage increases with time . a foreign body intruding the knee joint in childhood can go unnoticed initially and can cause symptoms for the first time in adult age . fragments can become adherent to the capsule or reside within synovial recesses or bursa without producing any symptoms for a very long time . symptoms are usually caused by the foreign bodies which are mobile within the knee joint , resulting in meniscal damage or recurrent locking episodes . in our case , the glass piece resided in the subcutaneous soft tissue for few days and later migrated into the knee joint to cause symptoms . late migration of other foreign bodies like bullets , broken arthroscopy probe tips into the knee joint have been reported in literature [ 7 , 8 ] . there is also a report of late migration of a glass piece of nearly 1.5 cm in size into the knee joint after remaining in the subcutaneous tissue for 7 years . arthroscopic removal of foreign bodies from the knee is a very simple procedure and has the advantages of avoiding large incision , shorter stay in the hospital faster recovery and reduced infection rates . glass foreign bodies were previously implicated in cartilage damage and meniscal injuries but a foreign body resulting in acl tear has not been reported in literature . a foreign body in the knee joint is an absolute indication for emergency arthroscopic surgery .
introduction : various types of foreign bodies have been removed from the knee joint . we report an unusual case of partial anterior cruciate ligament ( acl ) tear secondary to a glass foreign body in an adolescent knee joint.case report : a 13-year - old boy presented with pain , swelling and deformity of the left knee since 4 days . 
 x - ray revealed a foreign body in the left knee joint . 
 the glass foreign body remained in the subcutaneous tissue for few days and later migrated into the knee joint . 
 arthroscopy revealed partial tear in the acl at the femoral attachment with about 10 - 20 % of fibres being involved . 
 the glass piece was removed arthroscopically and the acl fibres were trimmed.conclusion:arthroscopic removal of foreign bodies from the knee is a very simple procedure and has the advantages of avoiding large incision , shorter stay in the hospital , faster recovery and reduced infection rates . 
 glass foreign bodies were previously implicated in cartilage damage and meniscal injuries but a foreign body resulting in acl tear has not been reported in literature .