Methods for enhancing joint function and for treating or preventing age-related joint discomfort in an adult human are disclosed. The methods comprise administering to the human a dietetic food, medical food, or food supplement. The food or food supplement comprises a rumenic acid-rich conjugated linoleic acid (RAR-CLA), or a pharmaceutically acceptable salt, ester, mono-, di-, or triglyceride, metabolic precursor thereof, or mixture thereof, in an amount effective to enhance joint function or to alleviate joint discomfort in the human. The RAR-CLA comprises cis-9, trans-11 linoleic acid and trans-10, cis-12 linoleic acid isomers in a weight ratio of at least 2:1. Enrichment of a dietetic food, medical food, or food supplement with RAR-CLA can help to improve joint function and/or alleviate joint discomfort. Longer-term studies should help to further elucidate the potential impact of RAR-CLA supplementation on joint function in older adults.