Knee pain is one of the most common causes of discomfort and limitation across all age groups and lifestyles—from casual walkers to competitive athletes. A frequent yet often misunderstood cause of persistent knee pain is knee tendinopathy, a condition that affects the tendons around the knee joint. These tendons are key players, connecting muscles to bones and enabling movement.

To fully grasp knee tendinopathy, it’s helpful to know that it develops in three distinct stages: reactive tendinopathy, tendon disrepair, and degenerative tendinopathy. Each stage involves different changes in the tendon tissue, varying symptoms, and unique treatment approaches. Understanding these stages is vital for patients and healthcare professionals alike, as it allows for tailored care that improves chances of recovery. Experts such as Professor Paul Lee, a leading cartilage specialist, and clinics like the London Cartilage Clinic provide excellent examples of care based on this staged model.

The Three Stages of Knee Tendinopathy: An Overview

Knee tendinopathy is best thought of as a progressive condition with three key phases. The first, known as reactive tendinopathy, usually follows a sudden overload or injury. The tendon swells and thickens but largely keeps its normal structure intact. Fortunately, this stage is often reversible with early and appropriate treatment.

If the strain continues, the condition can evolve into the second phase: tendon disrepair. Here, the collagen fibres within the tendon start to break down and become disorganised. The tendon tries to repair itself, but this attempt is imperfect and leads to increased pain and reduced function.

The final stage, degenerative tendinopathy, involves significant structural damage such as disruption of collagen fibres, cell death, and abnormal blood vessel formation. This results in ongoing pain and major functional problems, making treatment more challenging.

Knowing these stages helps doctors and physiotherapists to classify how advanced the tendinopathy is, adjust treatments accordingly, and better predict outcomes.

Recognising Signs and Symptoms at Each Stage

Knowing what to look out for can help you identify which stage of tendinopathy you might be experiencing and prompt you to seek the right care.

In the reactive stage, pain is usually sharp or aching and localised around the knee tendon, often soon after increased activity or overload. Swelling and thickening may be felt, but overall function tends to stay good, and stiffness is mild.

During tendon disrepair, the pain often becomes more persistent and worsens with use. Swelling is typically less obvious, but stiffness—especially in the morning or after rest—starts to appear. You might notice some difficulty with everyday tasks like climbing stairs.

By the time tendinopathy reaches the degenerative stage, the pain can be chronic, sometimes present even at rest. The tendon is tender to touch, stiffness is more severe, and performing simple actions such as standing up or walking can be noticeably hard.

It’s also important to understand that specific types of tendinopathy can influence symptoms and prognosis. For instance, quadriceps calcific tendinopathy (QCT), a condition seen mainly in advanced knee osteoarthritis, "could be considered an independent poor prognostic finding regarding pain, functional activity, and response to NSAIDs" (Mortada et al., 2021). This means such tendon changes often worsen pain and reduce your ability to function.

Research in sport shows that how you land or move can also affect tendon health. Among male amateur basketball players with patellar tendinopathy, “elevated patellar tendon force (PTF) may be linked to tendinopathy,” highlighting the role of tendon loading as a risk factor (Li et al., 2025).

By recognising typical symptoms and understanding these nuances, you can better communicate with healthcare providers and ensure the most appropriate care.

Understanding the Biological Changes

The symptoms you experience stem from important biological changes in the tendon tissue.

In the reactive stage, the tendon’s cells increase water content, causing swelling without breaking the important collagen fibres. This swelling is the tendon’s way of protecting itself and can usually be treated successfully if acted upon early.

When tendinopathy progresses to disrepair, tiny tears develop in collagen fibres, and the tendon tries to repair the damage by producing more but disorganised tissue. This stage also sees new, fragile blood vessels forming—a process linked with pain and reduced tendon flexibility.

Finally, the degenerative stage involves widespread tendon cell death and scar tissue formation. The tendon’s normal structure breaks down, leaving it weak and vulnerable.

A simple way to picture this is to imagine the tendon as a rope: in the reactive phase, it gets thicker but stays strong; in disrepair, some fibres fray; and in degeneration, many fibres snap and get replaced by weaker threads, reducing strength considerably.

How Imaging and Clinical Assessment Guide Treatment

Diagnosing the stage of knee tendinopathy is crucial and relies on a careful clinical assessment alongside modern imaging techniques.

Clinicians examine pain, tenderness, stiffness and how well you can move your knee. Specialists such as Professor Paul Lee use MRI and ultrasound scans to take a closer look at the tendon. MRI helps detect swelling and fibre damage, while ultrasound can show abnormal blood flow and tissue structure changes in real time.

Studies have shown that “QCT was found mainly in advanced knee osteoarthritis stages and mainly with ultrasonographic findings of CPPD disease," emphasising ultrasound’s role in identifying complex tendon issues (Mortada et al., 2021).

In addition, advanced biomechanical analysis is now helping to assess how movement patterns affect tendon load. For example, in basketball, “the OPLS-DA model effectively distinguished between players with and without patellar tendinopathy, suggesting applications in tendon health monitoring” (Li et al., 2025). This could be a breakthrough in identifying problems early, before symptoms become severe.

Combining clinical skills with imaging provides a clearer picture of your tendon health and allows treatment plans to be personalised.

Tailored Interventions and What to Expect as Knee Tendinopathy Progresses

Managing knee tendinopathy effectively depends on the stage of the condition.

In the reactive stage, treatment aims to reduce tendon overload and inflammation. This typically involves resting or modifying activity, along with gentle, guided exercises to rebuild strength without causing further harm.

As you progress into the disrepair stage, the focus shifts to encouraging healthy tendon healing. This may include careful, graduated loading exercises, shockwave therapy, or targeted injections. Multidisciplinary support from physiotherapists and sports medicine experts is often key.

Research confirms that “eccentric exercises demonstrated superior efficacy in reducing pain and improving function in chronic tendinopathies.” This means exercises where the muscle lengthens under load can be particularly effective in later stages (Szczypiór-Piasecka, 2025).

In the degenerative stage, treatment aims to manage chronic pain and improve function, although full tendon recovery is less likely. Exercise remains important, alongside other treatments such as platelet-rich plasma injections or surgery in severe cases. Setting realistic goals and supporting overall wellbeing become priorities.

Throughout all stages, expert guidance is crucial. Specialists like Professor Paul Lee and clinics like the London Cartilage Clinic deliver tailored care that addresses both physical healing and the psychological challenges of living with tendon pain.

Conclusion
Understanding the three stages of knee tendinopathy—reactive, disrepair, and degenerative—is key to improving knee health and recovery. Recognising your stage and seeking expert assessment allows for treatments tailored to your needs, boosting the chances of returning to pain-free activity. With the right care from experienced clinicians and specialist centres, better knee health is within reach.

Responsible Disclaimer: For individual medical advice, please consult a qualified healthcare professional.

References

• Szczypiór-Piasecka, K. (2025). Comparison of the effectiveness of eccentric and concentric exercises in orthopedic rehabilitation following tendinopathy, total knee and total hip arthroplasty. A literature review. Chirurgia Narządów Ruchu i Ortopedia Polska, 90(3), Article 5. https://doi.org/10.31139/chnriop.2025.90.3.5
• Mortada, M., Kotb, L. I., & Amer, Y. (2021). Impact of ultrasonography detected quadriceps calcific tendinopathy on pain and function in patients with primary knee osteoarthritis. Reumatismo, 73(3), Article 1381. https://doi.org/10.4081/reumatismo.2021.1381
• Li, F., Sun, D., Song, Y., Fang, Y., Cen, X., Zhang, Q., & Gu, Y. (2025). Comparison of landing biomechanics in male amateur basketball players with and without patellar tendinopathy during simulated games. Journal of Human Kinetics, 91, Article 201318. https://doi.org/10.5114/jhk/201318