How much pain is OK during rehab exercises? The pain traffic light

"Is it OK that it hurts when I do my exercises?" is one of the most common questions we hear at our clinic in North Tel Aviv - from runners with Achilles issues to patients weeks after ACL reconstruction. The short answer surprises many people: yes, some pain is usually acceptable, and within limits it is a normal part of recovery. This guide explains the Pain Monitoring Model - the traffic-light system used in rehabilitation research for over two decades - and exactly when to keep going, slow down, or stop.

What is the Pain Monitoring Model?

The Pain Monitoring Model is a research-tested framework that uses the 0-10 pain scale as a real-time thermometer for load. Instead of avoiding all pain - which weakens tendons and muscles - it defines a safe corridor: continue in the green zone, be cautious in yellow, stop in red.

The model was validated in a randomized controlled study by Silbernagel and colleagues (2007), where patients with Achilles tendinopathy continued sports activity using pain monitoring without harming their recovery. At the 5-year follow-up (2011), the majority had recovered fully with exercise alone. A pain-guided approach has also been tested in patellar tendinopathy (Sprague 2021). Full scientific sources are listed at the end of this article.

The traffic light: green, yellow, red

The 24-hour rule: the real test is not only during the exercise but the day after. If pain returns to your usual baseline within 24 hours, the dose was right. If it stays elevated, the dose was too high - even if it felt fine in the moment.

Does pain mean I am damaging the tissue?

No. Pain during rehab exercise is not a damage meter - it is a protective signal shaped by nervous-system sensitivity. Controlled, progressive loading inside the traffic-light limits is precisely what builds tendon and muscle capacity, while complete rest tends to weaken them over time.

This is why modern tendinopathy care has moved away from rest toward structured loading (Cook 2019; Escriche-Escuder 2020). Isometric and isotonic loading protocols are even used to reduce pain in patellar tendinopathy (Rio 2015; Vang 2021).

Is it different after surgery (ACL, knee or hip replacement)?

Yes - and this matters. After ACL reconstruction, meniscus repair or joint replacement, the limits are stricter: they follow the surgical protocol and tissue-healing timelines, not just the pain scale. The traffic light still helps you communicate with your physiotherapist, but surgical restrictions always win. If you are weeks after surgery and wondering whether a symptom is normal, that is exactly what your rehab team is for - see our ACL rehabilitation programme and post-surgery knee rehab.

Pain spiked mid-exercise? 4 steps

1. Step down a gear - less weight, fewer reps or smaller range, and check if pain drops back to green/yellow.
2. Check your tempo - slow, controlled reps; pain that spikes only on fast movement suggests uncontrolled load.
3. Finish light, do not quit - end with an easier version and note your pain number.
4. Apply the 24-hour rule next morning - settled: continue; still elevated: reduce the dose, and if the pattern repeats, update the plan with your physiotherapist.

When pain is a red flag - see a doctor, not a workout

The traffic light is for mechanical rehab pain. Chest pain or breathlessness on exertion, loss of strength or sensation, fever, constant night pain unchanged by position, or unusual swelling/redness/discharge after surgery - these are not a "colour", they are reasons to see a physician.

Frequently asked questions

Scientific sources

• Silbernagel KG, Thomeé R, Eriksson BI, Karlsson J. Continued sports activity, using a pain-monitoring model, during rehabilitation in patients with Achilles tendinopathy: a randomized controlled study. Am J Sports Med. 2007. DOI: 10.1177/0363546506298279 · PubMed
• Silbernagel KG, Brorsson A, Lundberg M. The majority of patients with Achilles tendinopathy recover fully when treated with exercise alone: a 5-year follow-up. Am J Sports Med. 2011. DOI: 10.1177/0363546510384789 · PubMed
• Sprague AL, Awokuse D, Pohlig RT, Cortes DH, Silbernagel KG. Pain-guided activity modification during treatment for patellar tendinopathy: a feasibility and pilot randomized clinical trial. Pilot Feasibility Stud. 2021. DOI: 10.1186/s40814-021-00792-5 · PubMed
• Rio E, van Ark M, Docking S, et al. Isometric Contractions Are More Analgesic Than Isotonic Contractions for Patellar Tendon Pain. Clin J Sport Med. 2017. DOI: 10.1097/JSM.0000000000000364 · PubMed
• Silbernagel KG, Hanlon S, Sprague A. Current Clinical Concepts: Conservative Management of Achilles Tendinopathy. J Athl Train. 2020. DOI: 10.4085/1062-6050-356-19 · PubMed
• Cook JL, Rio E, Docking SI, et al. Current trends in tendinopathy management. Best Pract Res Clin Rheumatol. 2019. DOI: 10.1016/j.berh.2019.02.001 · PubMed
• Escriche-Escuder A, Cuesta-Vargas AI, Casaña J. Load progression criteria in exercise programmes in lower limb tendinopathy: a systematic review. BMJ Open. 2020. DOI: 10.1136/bmjopen-2020-041433 · PubMed
• Ortega-Castillo M, Cuesta-Vargas AI, Luque-Suarez A. The role of progressive, therapeutic exercise in the management of upper limb tendinopathies: a systematic review. Musculoskelet Sci Pract. 2022. DOI: 10.1016/j.msksp.2022.102645 · PubMed
• Vang C, Niznik A. The Effectiveness of Isometric Contractions Compared With Isotonic Contractions in Patients With Patellar Tendinopathy. J Sport Rehabil. 2020. DOI: 10.1123/jsr.2019-0376 · PubMed

This content is educational and is not personal medical advice or a remote treatment prescription. Every rehabilitation plan is set in an individual assessment. When in doubt, see a physiotherapist or physician.