Analysis of cartilage creep-recovery of human osteoarthritic cartilage

Stolberg-Stolberg J; Löscher I; Charitou F; Huelskamp MD; Lang JJ; Köppe J; Lazic I; Tübel J; Burgkart R

Abstract

BACKGROUND: Articular cartilage of weight-bearing joints restores its thickness after loading through viscoelastic recovery. Creep-recovery is a key parameter for assessing cartilage biomechanical properties and is relevant for osteoarthritis (OA) diagnosis and cartilage replacement development. This study aimed to evaluate creep-recovery in human osteoarthritic cartilage. METHODS: Full-thickness osteochondral explants (n = 34) were obtained from tibial plateaus of 14 patients undergoing total knee replacement. Samples were graded histologically as normal (n = 6), mild (n = 18), moderate (n = 6), and severe OA (n = 4). Biomechanical testing was performed with a high-dynamic closed-loop indentation system using a porous indenter. Five creep-recovery cycles were applied under controlled load (0.01-0.196N); the third cycle was analyzed for creep, creep rate, recovery, recovery rate and stiffness. RESULTS: Normal and mild OA cartilage showed notably less creep strain than moderate OA (11.13 ± 3.84% vs. 12.45 ± 6.06% vs. 36.74 ± 25.75%; p < 0.05). Recovery after 60 s was 96.0 ± 2.8% in normal, 96.5 ± 5.0% in mild, and 95.8 ± 24.2% in moderate OA. Recovery rates were highest during the first second and significantly lower in moderate compared to normal and mild OA (p < 0.05). Severe OA samples displayed advanced degeneration, precluding biomechanical analysis. CONCLUSION: The viscoelastic recovery of human cartilage is significantly impaired in moderate OA, whereas normal and mildly degenerated tissue retain nearly complete restoration. Creep-recovery testing offers a sensitive functional marker for cartilage integrity and degeneration, supporting early detection of OA-related changes and evaluation of regenerative strategies.