Why Tendons and Ligaments Are a Collagen Story

Tendons and ligaments are, structurally, collagen tissue. Type I collagen makes up roughly 60 to 80 percent of the dry weight of a healthy tendon or ligament, organized into densely packed fibrils that give these tissues their tensile strength (Taye et al., 2020; Screen et al., 2015). When either structure is injured, sprained, or simply worn down by decades of loading, the rate-limiting step in recovery is the same: fibroblasts (cell type) have to synthesize new type I collagen, cross-link it properly, and remodel it into an organized matrix that can bear load again.

That biology is what makes collagen supplementation, most commonly sourced from bovine hide or bone, a reasonable question to ask in a tendon or ligament context. It is also why the claims made for it deserve the same scrutiny given to any other supplement. This piece works through what the research and the clinical trials actually show, where bovine-sourced collagen specifically fits in, and where the evidence is still thin.

Collagen and Tendon Repair: A Key to Recovery

Understanding Collagen and Tendon Repair is important for those involved in sports training or physical therapy, as it can directly impact recovery times and the effectiveness of treatments.

The Biological Rationale

Hydrolyzed collagen, whether from bovine, porcine, or marine sources, is broken down into short peptides dominated by glycine, proline, and hydroxyproline, the same amino acids that make up roughly half of collagen’s own amino acid sequence. The proposed mechanism is straightforward: ingested collagen peptides raise circulating levels of these amino acids and of specific di- and tripeptides (notably prolyl-hydroxyproline, or Pro-Hyp), providing both raw substrate and a signal that appears to stimulate fibroblasts to increase collagen gene expression (Shaw et al., 2017; Alcock et al., 2019).

This is different from the leucine-driven, mTOR-mediated pathway that stimulates muscle protein synthesis. Alcock and colleagues (2019), comparing plasma amino acid responses to dairy and collagen proteins in active men, describe the amino acids that collagen supplies as playing a supportive rather than stimulatory role in connective tissue synthesis: they provide building blocks at a time when synthetic machinery is upregulated by exercise, but the larger driver of tendon and ligament adaptation remains mechanical loading. Collagen supplementation is therefore best understood as an adjunct to loaded rehabilitation exercise, not a substitute for it.

Getting Collagen Peptides Into the Tissue: The Bioavailability Data

A 2024 randomized, double-blind crossover trial in Frontiers in Nutrition directly compared absorption of collagen hydrolysates from bovine hide, porcine skin, and fish skin in healthy volunteers. All three sources, including bovine hydrolysate tested at two molecular weights (2,000 and 5,000 Da), produced comparable increases in circulating Pro-Hyp and free hydroxyproline after a single 10-gram oral dose, with free hydroxyproline rising six- to nearly ten-fold above baseline within roughly 100 to 130 minutes (Virgilio et al., 2024). In other words, the animal source of the collagen made little difference to how efficiently the peptides reached the bloodstream. Bovine collagen’s practical advantage is availability, cost, and neutral flavor, not a demonstrated absorption edge over other sources.

The earlier study that established the exercise-timing protocol most trials now use came from Shaw, Lee, and colleagues (2017) at Keck School of Medicine. Eight men consumed vitamin C-enriched gelatin (0, 5, or 15 grams) one hour before intermittent rope-skipping exercise, repeated over three days. The 15-gram dose roughly doubled serum PINP, the propeptide marker of new type I collagen synthesis, compared with placebo, and the effect was dose-dependent across the three conditions. This single study is the basis for the now-common recommendation to take collagen with vitamin C about an hour before loading exercise or physical therapy.

Vitamin C’s Role as a Cofactor

Collagen synthesis cannot proceed normally without vitamin C, which is required by prolyl and lysyl hydroxylase, the enzymes that stabilize the collagen triple helix. A 2018 systematic review in Orthopaedic Journal of Sports Medicine found consistent preclinical evidence that vitamin C supplementation improves collagen structural quality and increases type I collagen content after tendon and ligament injury in animal models, alongside a protective antioxidant effect during the inflammatory phase of healing. Human clinical evidence was thinner and mixed: low-dose supplementation (around 60 mg per day) showed more consistent biomarker benefit than high-dose regimens (1,000 mg or more), and the review’s authors called for more rigorous human trials before firm dosing guidance could be issued (DePhillipo et al., 2018).

Clinical Evidence: Tendon Structure and Performance

The most rigorous body of evidence comes from studies combining collagen peptide supplementation with structured resistance training. Buchalski et al. (2026) pooled eight randomized controlled trials (257 participants total) that paired daily collagen doses of 5 to 30 grams with 3 to 15 weeks of resistance or plyometric training, published in Journal of Functional Morphology and Kinesiology. Findings were dose-dependent:

• Higher daily doses (15 to 30 grams) produced significantly greater increases in tendon cross-sectional area than training alone. Jerger et al. (2023) reported a 10.7 percent increase in patellar tendon CSA with collagen versus 6.5 percent with placebo after 14 weeks of resistance training (p = 0.010); Nulty et al. (2025) found a 6.1 percent increase versus no change in placebo (p = 0.027) in middle-aged men.
• Tendon stiffness and Young’s modulus improved more with collagen at higher doses. One 30-gram-per-day trial reported stiffness gains of 15.4 percent versus 4.6 percent in placebo (p < 0.001); another reported a 56.4 percent stiffness increase with a significant group interaction (p = 0.009).
• Lower doses (around 5 grams per day) showed improvement within the collagen group but did not reliably outperform placebo. Jerger et al.’s 2022 Achilles tendon trial, using 5 grams daily, found gains in both groups without a significant between-group difference.
• Pain was not a measured outcome in any of the eight structural/performance trials, and none of the pooled studies showed an additive strength benefit beyond training alone. The review graded evidence for tendon CSA (Cross-sectional area) and stiffness gains as strong (GRADE A), and evidence against added strength benefit as similarly strong.

Clinical Evidence: Injury and Post-Surgical Recovery

A narrative systematic review by Latini and colleagues, published recently  in Frontiers in Medicine (2026), specifically asked what evidence exists for collagen peptides in tendon and ligament tears, as opposed to healthy-tissue adaptation. It identified six eligible studies, three with direct evidence in tear or post-surgical populations and three with indirect evidence in related tendinopathy or instability populations:

• Latini et al. (2024), the same group’s own earlier work: a pilot, uncontrolled study of 21 patients with partial supraspinatus (rotator cuff) tears treated with ultrasound-guided intratendinous injection of low-molecular-weight hydrolyzed collagen peptides, reporting pain reduction and improved shoulder function at 12 weeks.
• Gumina et al. (2012): a randomized prospective trial of 90 patients following arthroscopic rotator cuff repair, using an oral combination of hydrolyzed type I collagen, arginine alpha-ketoglutarate, MSM, and bromelain, which reported improved postoperative pain control and lower analgesic use.
• López-Vidriero et al. (2019): a multicenter randomized controlled trial of 72 patients after ACL reconstruction, using an oral supplement combining collagen, hyaluronic acid, chondroitin sulfate, and plasma proteins, which reported reduced analgesic consumption and improved graft-maturation markers on imaging versus placebo.
• Praet et al. (2019), Dressler et al. (2018), and a 2023 observational study of subacromial collagen injection in rotator cuff tendinopathy provided indirect evidence in Achilles tendinopathy, chronic ankle instability, and rotator cuff tendinopathy respectively, generally reporting faster functional recovery with collagen peptide supplementation (oral or injected) alongside standard rehabilitation.

A separate randomized controlled trial outside that review examined injected collagen peptides for collateral ligament pain. Sixty-two patients with confirmed ligament inflammation at the knee were randomized to a single peri-ligamentous injection of hydrolyzed collagen peptides (under 3,000 Da) plus oral analgesics, or corticosteroid injection plus oral medication. The collagen group showed significantly better pain and function scores (VAS and WOMAC) at 3 and 6 months, though ultrasound imaging showed similar structural healing between groups, and patient satisfaction was higher with collagen with no adverse effects reported (Luu Thi et al., 2023).

A well-designed, adequately powered trial specifically built to test hydrolyzed collagen plus vitamin C for patellar tendinopathy (the JUMPFOOD study, a 76-athlete double-blind RCT using 10 grams of hydrolyzed type I collagen with 40 mg vitamin C over 24 weeks) began recruiting in 2023, with results not yet published as of this writing. It is worth watching, because it is designed to correct several weaknesses in the existing literature: adequate blinding, a single well-defined active ingredient rather than a multi-ingredient blend, and validated outcome measures (van Dam et al., 2023).

Where the Evidence Is Genuinely Strong, and Where It Isn’t

Taken together, three claims are reasonably well supported:

1.) Oral collagen peptides are absorbed efficiently regardless of animal source, and bovine-derived collagen performs comparably to porcine or marine collagen in raising circulating collagen-building peptides.

2.) In healthy tendon, 15 to 30 grams of collagen daily, combined with resistance training and taken roughly an hour before loading, produces measurably greater increases in tendon size and stiffness than training alone. This is the best-controlled body of evidence in the field.

3.) Vitamin C is mechanistically necessary for the collagen cross-linking that supplementation is meant to support, even though the human dosing evidence for vitamin C on its own is still limited.

Two claims are weaker than marketing copy often suggests:

1.) Evidence that collagen supplementation meaningfully speeds healing of an actual tendon or ligament tear, as opposed to adapting already-healthy tissue, is described by its own most recent systematic review as “sparse, heterogeneous, and low certainty” (Latini et al., 2026). Most of the positive tear-related trials used multi-ingredient formulas (collagen plus MSM, bromelain, hyaluronic acid, or arginine), which makes it impossible to attribute the benefit to collagen specifically. Sample sizes were small, several trials lacked blinding or a true placebo, and pain was rarely a primary outcome.

2.) No trial to date has shown that collagen supplementation adds strength beyond what resistance training alone produces, and none has demonstrated a reduction in reinjury rates with the statistical power to be conclusive.

For a client or reader asking whether bovine collagen is worth taking for tendon or ligament health, the honest answer sits between “yes it helps” and “it’s useless.” The most defensible, evidence-aligned protocol looks like this:

1.) Dose in the range shown to work in controlled trials: 15 grams daily was the effective threshold in the Shaw et al. synthesis study; the tendon-adaptation trials that produced significant structural gains used 15 to 30 grams daily.

Practical Takeaways

2.) Pair it with 50 to 100 mg of vitamin C, and take it roughly 30 to 60 minutes before the loading exercise or rehabilitation session, not at an unrelated time of day.

3.) Treat it as an adjunct to, never a replacement for, progressive tendon-loading exercise. Every positive structural finding in this literature occurred alongside a structured training or rehabilitation program, not collagen taken in isolation.

4.) Set expectations accordingly for an actual tear or post-surgical repair. The signal there is cautiously positive but far from settled, and current evidence does not support collagen as a stand-alone treatment for an existing tendon or ligament injury.

References

Alcock, R. D., Shaw, G. C., Tee, N., & Burke, L. M. (2019). Plasma amino acid concentrations after the ingestion of dairy and collagen proteins, in healthy active males. Frontiers in Nutrition, 6, 163. https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2019.00163/full

Buchalski, A., Jeanfavre, M., Altorelli, C., & Leff, G. (2026). Collagen supplementation on tendon-related structural and performance outcomes: A systematic review. Journal of Functional Morphology and Kinesiology, 11(1), 130. https://www.mdpi.com/2411-5142/11/1/130

Buda, R., et al. (2023). Subacromial injection of hydrolyzed collagen in the symptomatic treatment of rotator cuff tendinopathy: An observational multicentric prospective study on 71 patients. JSES International. https://jsesinternational.org/article/S2666-6383(23)00155-X/fulltext

DePhillipo, N. N., Aman, Z. S., Kennedy, M. I., Begley, J. P., Moatshe, G., & LaPrade, R. F. (2018). Efficacy of vitamin C supplementation on collagen synthesis and oxidative stress after musculoskeletal injuries: A systematic review. Orthopaedic Journal of Sports Medicine, 6(10). https://journals.sagepub.com/doi/10.1177/2325967118804544

Dressler, P., et al. (2018). Improvement of functional ankle properties following supplementation with specific collagen peptides in athletes with chronic ankle instability. Journal of Bodywork and Movement Therapies, 22(4), 858. https://pubmed.ncbi.nlm.nih.gov/29769831/

Gumina, S., Passaretti, D., Gurzì, M. D., & Candela, V. (2012). Arginine L-alpha-ketoglutarate, methylsulfonylmethane, hydrolyzed type I collagen and bromelain in rotator cuff tear repair: A prospective randomized study. Current Medical Research and Opinion, 28(11). https://pubmed.ncbi.nlm.nih.gov/23043451/

Jerger, S., et al. (2022). Effects of specific collagen peptide supplementation combined with resistance training on Achilles tendon properties. Scandinavian Journal of Medicine & Science in Sports. https://onlinelibrary.wiley.com/doi/10.1111/sms.14164

Jerger, S., et al. (2023). Specific collagen peptides increase adaptations of patellar tendon morphology following 14 weeks of high-load resistance training: A randomized-controlled trial. European Journal of Sport Science. https://www.tandfonline.com/doi/full/10.1080/17461391.2023.2232758

Latini, L., Porta, F., Maccarrone, V., Zompa, D., Cipolletta, E., Mashadi Mirza, R., Filippucci, E., & Vreju, F. A. (2024). Clinical efficacy and safety of ultrasound-guided injection with low-molecular-weight peptides from hydrolyzed collagen in patients with partial supraspinatus tendon tears: A pilot study. Life, 14(11), 1351. https://www.mdpi.com/2075-1729/14/11/1351

Latini, L., Porta, F., Vitale, N., Vreju, F. A., & Filippucci, E. (2026). Clinical evidence for low-molecular-weight collagen peptides in tendon and ligament tears: A systematic review with narrative synthesis. Frontiers in Medicine, 13. https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2026.1891011/full

López-Vidriero, E., Olivé-Vilas, R., López-Capapé, D., Varela-Sende, L., López-Vidriero, R., & Til-Pérez, L. (2019). Efficacy and tolerability of Progen, a nutritional supplement based on innovative plasma proteins, in ACL reconstruction: A multicenter randomized controlled trial. Orthopaedic Journal of Sports Medicine, 7(9). https://doi.org/10.1177/2325967119827237

Luu Thi, B., Tran Thi, L., & Hoang Thi, M. H. (2023). Effectiveness of hydrolyzed collagen peptide injection for the treatment of collateral ligament pain: A randomized controlled trial. Journal of Clinical & Medical Surgery, 3(2), 1127. https://jclinmedsurgery.com/articles/jcms-v3-1127.html

Praet, S. F. E., Purdam, C. R., Welvaert, M., Vlahovich, N., Lovell, G., Burke, L. M., Gaida, J. E., Manzanero, S., Hughes, D., & Waddington, G. (2019). Oral supplementation of specific collagen peptides combined with calf-strengthening exercises enhances function and reduces pain in Achilles tendinopathy patients. Nutrients, 11(1), 76. https://pubmed.ncbi.nlm.nih.gov/30609761/

Screen, H. R. C., Berk, D. E., Kadler, K. E., Ramirez, F., & Young, M. F. (2015). Tendon functional extracellular matrix. Journal of Orthopaedic Research, 33(6). https://onlinelibrary.wiley.com/doi/full/10.1002/jor.22818

Shaw, G., Lee-Barthel, A., Ross, M. L. R., Wang, B., & Baar, K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. The American Journal of Clinical Nutrition, 105(1), 136–143. https://ajcn.nutrition.org/article/S0002-9165(22)04737-2/fulltext

Taye, N., Karoulias, S. Z., & Hubmacher, D. (2020). The “other” 15–40%: The role of non-collagenous extracellular matrix proteins and minor collagens in tendon. Journal of Orthopaedic Research, 38(1), 23–35. https://onlinelibrary.wiley.com/doi/full/10.1002/jor.24440

van Dam, A., et al. (2023). The JUMPFOOD study: Additional effect of hydrolyzed collagen and vitamin C to exercise treatment for patellar tendinopathy (jumper’s knee) in athletes, study protocol for a double-blind randomized controlled trial. Trials, 24, 768. https://link.springer.com/article/10.1186/s13063-023-07783-2

Virgilio, N., Schön, C., Mödinger, Y., van der Steen, B., Vleminckx, S., van Holthoon, F. L., Kleinnijenhuis, A. J., Silva, C. I. F., & Prawitt, J. (2024). Absorption of bioactive peptides following collagen hydrolysate intake: A randomized, double-blind crossover study in healthy individuals. Frontiers in Nutrition, 11, 1416643. https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2024.1416643/full

Note on sourcing: entries listed with “et al.” reflect the level of author attribution available in the secondary sources consulted during research (their first author is confirmed; full co-author lists were not independently verified). Links go to each study’s PubMed listing or publisher page; where PubMed’s own page for a title returned inconsistent journal metadata during research (noted for the Dressler et al. 2018 entry, corrected here to Journal of Bodywork and Movement Therapies), the publisher-confirmed citation is used in the text with the PubMed link kept for convenience.