Understanding Tendons: Function, Health, and Care

​The anatomy of a tendon

A tendon is a cord of strong, flexible tissue (similar to a rope) that connects muscle to bone. Tendons transmit the forces produced by the muscles to the skeleton, creating movement and supporting the joint posture. They also help prevent muscle injury by absorbing some of the impact your muscles take when you run, jump or do other high energy movements.

Tendons are much stiffer than muscles and have greater tensile strength, this means they can withstand larger pressures with minimal distortion. For example, tendons of the foot can bear more than eight times our own body weight and store about 40% of this weight to aid propulsion during walking.

A tendon is mainly made up of collagen (type I), elastin and water. The collagen fibres in a healthy tendon are arranged longitudinally to best absorb the forces placed upon them.

Tendon injury

The most common areas for tendon injury are around the shoulders, elbows, hips, knees and ankles. You may have heard of Achilles tendonitis, Tennis elbow, Golfer’s elbow, Runner’s knee and Rotator cuff tendinopathy.

Tendons are vulnerable to:
- Compression and direct trauma
- Stretch and tearing injuries
- Tendon rupture, a full tear
- Inflammatory injury, aka tendonitis
- Repetitive strain injury, aka tendinopathy

Tendonitis and tendinopathy are similar terms and are both conditions affecting tendons, but they are quite different in nature.

Tendonitis involves acute inflammation of a tendon due to injury or short-term overuse, resulting in pain and swelling. This is typically treated with rest and physical therapy.

Tendinopathy, on the other hand, is a chronic condition characterized by tendon degeneration from prolonged overuse, leading to persistent pain, stiffness and weakness. Treatment for tendinopathy focuses on rehabilitation, physical therapy and exercises to promote tendon healing and strength. A tendinopathy will typically take longer to heal than a tendonitis.

In many cases a severe tendon tear or full tendon rupture would require a surgical fix. Small tears or partial tears can be managed with physical therapies such as Osteopathy and Physiotherapy.

Predisposing factors for injury are:

1. Age – there is a reduced capacity for regeneration and repair with age. Also often a decrease in strength and activity.
2. Gender – research shows that when subjected to repeated mechanical stress, females develop less tendon strength than males.
3. Hormones – decreasing oestrogen levels loosen the tendon tissues, making them more susceptible to injury and inflammation. Naturally, this affects females more than males and becomes most noticeable post menopause due to the hormonal shifts.
4. Obesity – Being overweight and having a lower baseline strength increases the mechanical load on our tendon. Poor nutrition will also impact the health of our tendons and their ability to repair from trauma.
5. Chronic disease and inflammatory conditions - such as rheumatoid arthritis, diabetes, spondyloarthropathies, high cholesterol, and lupus all include an increased risk of tendon issues.
6. Medications – certain medications have been linked to an increased risk of tendon injury, two examples are corticosteroids and statins.
7. Smoking – Smokers are 1.5 times more likely to suffer overuse tendon injuries vs nonsmokers.
8. Repetitive strain (RSI) – Manual workers, office workers, athletes and sportspeople are more likely to experience repetitive strain injuries due to the nature of certain tasks within their work.

Tendon repair and rehabilitation simplified

Tendon repair happens in three main phases:

1. Inflammation (first 48 hours):
- Blood cells and enzymes rush to the injury.
- White blood cells called macrophages clean up any debris and infection.
- Swelling and bruising occur, and pain receptors activate to prevent us causing any further damage.

2. Proliferation (7-21 days):
- New, but weaker collagen (type III) forms in disorganised manner to begin repairing the tendon.
- New blood vessels grow to restore circulation.
- Swelling and bruising reduces, and pain levels decrease.

3. Remodelling (21 days to 1 year+):
- Stronger collagen (type I) slowly replaces the weaker collagen.
- Tendon fibres re-align to handle stress better, reaching up to 80% of their original strength.

The stages of tendon rehabilitation:

Goal #1 - Reduce pain and control inflammation
- Avoid activities that stress the tendon.
- Introduce simple isometric exercises.
- Find and correct any postural and compensatory issues that may have predisposed the original injury.

Goal #2 – Start to rebuild strength of injured tissues
- Progress the rehabilitation to include simple and controlled resistance training
- Allow rest days for recovery.
- Improve global movement and strength patterns to reduce the stress on the injured tendon.
- Remain patient, strength gains take 6-8 weeks for muscles and 3-4 months for tendons.

Goal #3 – Restore functional movement
- Advance the rehabilitation program to be more functional, reflecting the more complex needs of day-to-day activity.
- Add in more dynamic movements and stretching.

Goal #4 – Gradual return to sport
- A gradual reintroduction to sport-specific activities.
- Ensure you can perform all exercises without pain before fully returning to competitive sports.

The timeline and progression of these stages will vary depending on the severity of injury, ability to avoid aggravating activities, general health, age and an individual’s commitment to physical therapy and compliance in the rehabilitation program set.

Nutrition and tendon health

A summary of recent studies highlights the significant role of nutrition in tendon healing.

• Taking vitamin C can boost collagen production and speed up recovery from tendonitis.
• Omega-3 fatty acids, according to a study on rats, reduces inflammation, enhances collagen synthesis, and helps tendons heal faster.
• Getting enough zinc and magnesium also supports collagen production and overall tendon health.
• Additionally, a review found that combining collagen peptide supplements with exercise can help tendinopathy patients recover more quickly.

Overall, a healthy diet and proper nutrition provides the essential building blocks for tissue repair and helps to reduce inflammation, thus enhancing the body's healing potential.