The effects of short-term non-weightbearing and immobilization after anterior cruciate ligament reconstruction on articular cartilage: Long-term observation after reloading and remobilization

Non-weightbearing or immobilization after anterior cruciate ligament (ACL) reconstruction accelerates cartilage degeneration. However, it is unclear whether these adverse effects are reversed by reloading or remobilization. Moreover, it is unknown whether the combination of non-weightbearing and immobilization after ACL reconstruction has synergistic effects on cartilage degeneration. We aimed to determine 1) the long-term effects of reloading or remobilization following short-term non-weightbearing or immobilization after ACL reconstruction on cartilage degeneration and 2) the combined effects of non-weightbearing and immobilization on cartilage degeneration. We divided ACL-reconstructed rats into four groups: no intervention, non-weightbearing, joint immobilization, and non-weightbearing plus immobilization. Non-weightbearing and immobilization were performed for 2 weeks, after which all rats were reared without intervention. Untreated rats were used as controls. At 2, 4, or 12 weeks after starting the experiment, cartilage degeneration in the anterior, middle, and posterior regions of the medial tibial plateau was histologically assessed. Two weeks of non-weightbearing or immobilization after ACL reconstruction facilitated cartilage degeneration in the middle and posterior regions compared to those with no intervention. Cartilage degeneration was not reversed by 10 weeks of reloading or remobilization. Compared with non-weightbearing alone, combination of non-weightbearing and immobilization improved cartilage degeneration in the middle region, but worsened it in the posterior region. Cartilage degeneration induced by 2 weeks of non-weightbearing or immobilization after ACL reconstruction was not reversed by reloading or remobilization. Thus, to reduce cartilage degeneration, non-weightbearing and immobilization should be avoided after ACL reconstruction, even for short-term.