PROBLEM TO BE SOLVED: To provide a cartilage function-improving agent, which can be taken on a daily basis for a long time, promotes the proliferation of chondrocytes, and/or has an effect of suppressing calcification of chondrocytes, and is useful for the prevention and treatment of various joint diseases, such as osteoarthritis, particularly knee osteoarthritis, and also provide a cartilage function-improving food or drink, cartilage function-improving nutritional composition, and cartilage function-improving feed, which contain the cartilage function-improving agent.SOLUTION: According to the present invention, a cartilage function-improving agent comprises, as an active ingredient, at least one selected from lactoperoxidase, cystatin, HMG-like protein, and/or degradation products thereof, which are proteins contained in milk and dairy products. The cartilage function-improving agent of the present invention has remarkable effects of correcting or regenerating deformed or disappeared cartilage, and is therefore useful for prevention and treatment of various joint diseases, such as osteoarthritis, particularly osteoarthritis of the knee.SELECTED DRAWING: Figure 1【課題】日常的に安全に長期間摂取することが可能であり、軟骨細胞の増殖を促進する、及び／又は、軟骨細胞の石灰化を抑制する作用を有し、変形性関節症、特に、変形性膝関節症などの種々の関節疾患の予防や治療に有用な軟骨機能改善剤及び、軟骨機能改善剤を配合した軟骨機能改善用飲食品、軟骨機能改善用栄養組成物、軟骨機能改善用飼料を提供することを課題とする。【解決手段】牛乳、乳製品に含まれるタンパク質であるラクトパーオキシダーゼ、シスタチン、ＨＭＧ様タンパク質、及び／又は、それらの分解物から選択されるいずれか１種類以上を有効成分とする軟骨機能改善剤。本発明の軟骨機能改善剤は、変形あるいは消失した軟骨を修正または再生する効果が顕著であるため、変形性関節症、特に、変形性膝関節症などの種々の関節疾患の予防や治療に有用である。【選択図】図１
