In vivo changes after mechanical injury

Chondrocytes undergo apoptosis in response to mechanical injury in vitro. T he current clinical study correlates arthroscopic and magnetic resonance im aging results with biopsy specimens of cartilage from patients with knee in jury. Twenty patients were evaluated at a mean 2.7 months after acute knee injury. The mean age of the patients was 32 years and the mean weight was 8 3 kg. Cartilage lesions were graded separately on magnetic resonance images and arthroscopy in a blinded manner. During arthroscopy, a 1.8 mm diameter biopsy specimen was obtained from the edge of cartilage lesion. The biopsy specimen underwent histologic examination by safranin O staining and detec tion of chondrocyte apoptosis by the presence of deoxyribonucleic acid frag mentation. There was a positive correlation in 50% (10 of 20) when the pres ence or absence of cartilage lesions by magnetic resonance imaging was corr elated with arthroscopy. All cases of partial thickness or full-thickness c artilage loss that were seen by arthroscopy also were detected by magnetic resonance images. Apoptotic cells were significantly more numerous in biops y specimens from lesions compared with control biopsy specimens. The findin gs of reduced cell viability attributable to apoptosis may have profound im plications for cartilage repair. This opens potential therapeutic avenues f or the treatment of posttraumatic cartilage lesions through apoptosis preve ntion.