Hydrolyzed beef collagen is promoted as a dietary supplement to support joint health, including the knees, largely based on its role as a source of collagen peptides. Collagen is a major structural protein in connective tissues, including cartilage found in joints. Several randomized controlled trials have investigated oral collagen supplementation in individuals with osteoarthritis or joint pain, often focusing on hydrolyzed collagen from bovine or porcine sources.

Some studies have shown modest improvements in joint pain and function with daily supplementation (typically 5-10 grams per day) over periods of 8-24 weeks. For example, a 2012 double-blind, placebo-controlled study found that athletes with joint pain experienced improvements in joint discomfort after 24 weeks of hydrolyzed collagen supplementation. Meta-analyses suggest a small but statistically significant benefit for pain reduction in osteoarthritis, but the clinical significance is debated. The mechanism is hypothesized to involve the absorption of collagen peptides, which may stimulate extracellular matrix production in cartilage via chondrocyte activity. However, not all studies find benefit, and the quality of evidence is limited by small sample sizes, study heterogeneity, and industry sponsorship.

There is no robust evidence that hydrolyzed beef collagen can “strengthen” weak knees in the absence of diagnosed joint disease. Most supporting data are for symptomatic relief of osteoarthritis or exercise-induced joint discomfort, rather than prevention or treatment of underlying structural weakness.