ochronosis is seen mostly in adults and peaks in the forth decade . with increasing age complaints of hip ,
although ochronotic pigmentation of tissues , black discoloration of urine due to sodium hydroxide ( naoh ) , degenerative arthropathy of large joints are classical findings , definitive diagnosis is made with quantitative detection of homogentisic acid in the urine and detection of ochronotic pigmentation in the histopathologic examination of tissue biopsies . in this paper
we present a case complaining of knee pain and having arthroscopically detected black discoloration of menisci and cartilage which led us to the biopsy and further laboratory tests and finally diagnosed as ochronosis .
a forty two year - old male admitted to our outpatient clinic with right knee pain and clicking on exertion for two years .
there was pain on the lateral joint line by palpation and mc murray test was positive .
x - ray revealed arthrosis in the lateral tibiofemoral and patellofemoral joint spaces . magnetic resonance imaging ( mri ) of the right knee revealed effusion , partially torn anterior cruciate ligament , thickening of quadriceps tendon .
there were 3  cm    2  cm in diameter outerbridge stage 4 chondral defect in patellar joint surface and medial femoral condyle .
1 ) . acl was partially torn but the posterior cruciate ligament ( pcl ) was intact .
arthroscopic view of the lateral joint space revealed a large , yellow and black colored grade 4 chondral defect in the lateral tibial condyle .
lateral meniscus was thickened , black colored at the inferior surface and torn ( fig .
biopsy was taken from the black colored areas of femoral condyle ( fig . 3a and b ) .
we have done further investigation with the suspect of ochronosis because of the black discoloration of tissues seen in the arthroscopic intervention .
urine was normal in color but when treated with sodium hydroxide ( naoh ) color of the urine became darker ( fig .
the patient is under follow up by cardiology for valvular insufficiency and orthopedics for ochronotic arthropathy .
it was first described by virchow in a postmortem examination of a 67 year - old patient in 1866 .
it is characterized by deposition of ochronotic pigment in the tissues due to homogentisic oxidase enzyme deficiency in the tyrosine metabolism .
ochronotic pigment can accumulate in hyaline cartilage , tendon , skin , teeth , nail , sclera , tympanic membrane , heart valves , renal tubular cells , duramater , pancreas and walls of great arteries .
ochronosis is easily recognized with ochronotic pigmentation of tissues , degenerative arthropathy , especially in large joints and dark discoloration of urine because of alcalinisation .
all patients in the literature were examined with knee arthroscopy with different reasons and the diagnosis of ochronosis is made through a further investigation of the intraarticular tissues because of the black discoloration . as in the other cases , black discoloration of cartilage and meniscal tissues
moreover , we detected osteoarthritis and vacuum phenomenon in the intervertebral joints , arthrosis of large joints like hip , knee and glenohumeral joints and increased homogentisic oxidase in urine . unlike other cases we detected thickening of quadriceps tendon and asymptomatic supraspinatus tear in the mri and mitral valve insufficiency as an extraarticular finding . increasing homogentisic acid levels in the blood and resulting accumulation in tissues become symptomatic especially in the forth decade along with decreasing renal functions .
in ochronotic arthropathy , articular cartilage becomes more sensitive to mechanic stresses causing fragmentation and resulting in nonspecific tenosynovitis .
high grade glenohumeral arthropathy is very rare but must be kept in mind in ochronotic arthropathy .
homogentisic acid polyphenol oxidase enzyme , which is located especially in tendons and ligaments , produces free radicals through oxidation and causes tendon and ligament ruptures .
mri of our patient revealed partial rupture of acl , a thickened quadriceps tendon and asymptomatic rupture of supraspinatus tendon .
high dose ascorbic acid ( 100  mg / kg ) may reduce hga excretion in the urine but does not prevent development of arthropathy . because the modalities addressing the cause of the disease are unclear , treatment of ochronotic arthropathy is symptomatic .
nonsteroid antiinflammatory drugs and preparates containing glucosamine and chondroitin sulphate , intraarticular hyaluronic acid and steroid injections , arthroscopic debridement and arthroplasty are the treatment options .
arthroscopy is helpful in diagnosis of ochronotic arthropathy and may lead to further investigation and treatment of concomitant pathologies .
written informed consent was obtained from the patient for publication of this case report and case series and accompanying images .
a copy of the written consent is available for review by the editor - in - chief of this journal on request .
adnan kara : study concept or design , data collection , data analysis or interpretation , writing the paper .
hasan basri sezer : writing the paper.bekir eray kilinc : writing the paper.metin uzun : writing the paper.key learning pointochronosis is a rare disease affecting connective tissues .
arthroscopy is helpful in diagnosis of ochronotic arthropathy and may lead to further investigation and treatment of concomitant pathologies .
arthroscopy is helpful in diagnosis of ochronotic arthropathy and may lead to further investigation and treatment of concomitant pathologies .
arthroscopy is helpful in diagnosis of ochronotic arthropathy and may lead to further investigation and treatment of concomitant pathologies .
 introductionochronosis is a rare disorder which is defined as the deposition of metabolites of oxidation and polymerization of homogentisic acid , which have high affinity to collogen , in the connective tissues . 
 it is a clinical condition characterized with ochronotic pigmentation of tissues , degenerative arthropathy of especially large joints and black discoloration of urine . in this paper 
 we present a case of ochronosis diagnosed with biopsy and additional tests when a black discoloration of menisci and joint cartilage were detected during arthroscopic intervention for a degenerative meniscus tear.presentation of casea forty two year - old male patient was operated for lateral meniscus tear of his right knee . 
 the arthroscopic examination of right knee revealed black colored synovial hypertrophy and torn lateral meniscus . 
 partial meniscectomy was performed . 
 the diagnosis of ochronosis was made after histopathologic examination.discussionochronotic pigment can accumulate in hyaline cartilage , tendon , skin , teeth , nail , sclera , tympanic membrane , heart valves , renal tubular cells , duramater , pancreas and walls of large arteries . in ochronosis 
 the most frequently involved joints are knee and hip . in ochronotic arthropathy , articular cartilage become more sensitive to mechanical stresses . 
 our patient had meniscal tear , cartilage damage and black discoloration of synovial tissues and meniscus.conclusionarthroscopy may be helpful in diagnosis of ochronotic arthropathy . 
Introduction
Presentation of case
Discussion
Conclusion
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