Ochronosis diagnosed after knee arthroscopy

Abstract

Introduction: Ochronosis 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 case: A 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.

Discussion: Ochronotic 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.

Conclusion: Arthroscopy may be helpful in diagnosis of ochronotic arthropathy.

Keywords: Arthroscopy; Knee; Ochronosis.

Fig. 1

Chondral lesion on medial femoral condyle.

Fig. 2

Arthroscopic vision of torn lateral meniscus.

Fig. 3

Bone biopsy specimen shows the dark discoloration of the bony surface.

Fig. 4

The normal colored urine of the patient turned in to black after treatment with sodium hydroxide.