What is a tendon?
A tendon is a cord of strong, flexible tissue, similar to a rope. Tendons connect your muscles to your bones. Tendons let us move our limbs. They also help prevent muscle injury by absorbing some of the impact your muscles take when you run, jump or do other movements.
Your body contains thousands of tendons. You can find tendons from your head all the way down to your toes. The Achilles tendon, which connects your calf muscle to your heel bone, is the largest tendon in your body.
Tendons are highly resistant to tearing but aren’t stretchy. This means they can be easily injured when strained (stretched to point partial tearing of rope fibers) and may take a long time to heal.
What does a tendon do?
When you contract (squeeze) your muscle, your tendon pulls the attached bone, causing it to move. Tendons essentially work as levers to move your bones as your muscles contract and expand.
Tendons are stiffer than muscles and have great strength. For instance, the flexor tendons in your foot can handle more than eight times your body weight.
Where are your tendons?
Tendons are located all over your body. For instance, tendons connect your muscles to your bones in your elbow, heel, knee, shoulder and wrist.
How big are tendons?
Tendons have different shapes and sizes depending on which muscles they’re attached to. Wider and shorter tendons usually connect to muscles that generate a lot of force. Thinner and longer tendons usually connect to muscles that perform more delicate movements.
What is the anatomy of a tendon?
Tendons are mostly collagen, one of the most abundant proteins in your body. Tendons also contain blood vessels and nerves.
Collagen fibers are flexible, strong and resistant to damage. A tendon’s structure is similar to a fiberoptic cable or a rope, with small collagen fibers arranged in bundles. This bundling reinforces the tendon and makes it stronger.
The collagen fibers in a tendon group into:
- Primary fiber bundles (subfascicles), the smallest bundle.
- Secondary fiber bundles (fascicles) made of groups of subfascicles.
- Tertiary (third) fiber bundles containing groups of fascicles that form the tendon itself.
What are the parts of a tendon?
A tendon consists of:
- Endotenon: Connective tissue that surrounds the primary, secondary and tertiary fiber bundles. Helps the bundles glide against each other inside the tendon.
- Epitenon: Thin layer of connective tissue that surrounds the entire tendon.
- Paratenon: Loose layer of connective tissue that lets the tendon move against the epitenon and other tissues that the tendon touches. Located outside the epitenon.
- Sharpey fibers: Collagen fibers that attach the tendon to the bone.
- Sheath (synovium): Some tendons in the hand and foot have a sheath (synovium). This is the protective outer covering of the tendon. Produces a lubricating fluid called synovial fluid, which helps the tendon slide smoothly where it meets muscle and bone.
How do tendons connect muscles to bones?
Tendons connect your muscles to your bones at the following points:
- Musculotendinous junction (MTJ): The point where the tendon attaches to your muscle. Note this is a frequent site of injury.
- Osteotendinous junction (OTJ): The point where the tendon attaches to your bone.
The Sharpey fibers that are part of the tendon extend into the bone. The tendon of the hand and foot commonly slides through a connection called a reflection pulley that helps hold it in place. Small, fluid-filled pads called tendon bursae (plural of bursa) cushion tendons where they meet the bone.
Conditions and Disorders
What conditions and disorders can affect tendons?
Because tendons connect every muscle in your body, a wide range of injuries and disorders can cause tendon problems. Tendon issues are more common with age. As people get older, tendons become thinner, have less blood flow and accumulate microscopic damage to fibers that weaken the tendon.
Most commonly, disorders that affect the tendons include:
Strains: Strains occur when you tear, twist or pull a tendon. Tendon strains often happen in your arms and legs.
Tendonitis: Tendonitis results when your tendons become inflamed, usually due to repetitive activities, overuse or aging. Tendonitis (also called tendinitis) often occurs in your Achilles tendon, elbow, hip, knee, shoulder or thumb. The most common types of tendonitis include:
- Patellar tendonitis: Patellar tendonitis happens when you injure the tendon that connects your kneecap (patella) to your shinbone (tibia). This condition usually results from overuse.
- Rotator cuff tendonitis: Rotator cuff tendonitis occurs when shoulder muscles become inflamed. This condition can be due to repetitive activities or injury.
- Tennis elbow (lateral epicondylitis): Tennis elbow results when you microscopically tear the tendons around the outside of your elbow. Overuse of your forearm muscles can cause tennis elbow.
Tenosynovitis: Tenosynovitis occurs when tendinitis combines with inflammation of the tendon sheath. This commonly occurs in the hand and feet. Two common types are:
- DeQuervain’s tenosynovitis: DeQuervain’s tenosynovitis causes swelling in the thumb tendons. It can result from overuse, repetitive grasping or inflammatory conditions, such as arthritis.
- Trigger finger or trigger thumb: Trigger finger or trigger thumb occurs when your finger or thumb becomes stuck in a bent position. Inflamed and irritated tendons cause this condition.
Other tendon disorders include:
- Biceps tendon injuries: Biceps tendon injuries occur due to microtears in the tendon. They can occur in the shoulder or elbow due to repetitive motion or injury.
- Posterior tibial tendon dysfunction: The posterior tibial tendon supports your foot when you walk. It can tear or become inflamed due to injury or overuse. This tendon connects your calf muscle to the bones on the inside of your foot.
- Rotator cuff tears: Rotator cuff tears happen when your shoulder tendons partially of fully detach from the upper part of your arm bone (humerus). These tears may be due to injury or overuse.
- Tendinosis: Tendinosis, a chronic condition, occurs when collagen in your tendons has accumulated many torn fibers within the tendon which weakens the tendon thus deteriorates the tendon structure. Tendon overuse causes tendinosis. It most commonly happens in the elbow, heel, knee, shoulder or wrist.
What tests can check the health of your tendons?
Your healthcare provider will first do a physical examination. The key components are evaluating the joints connected by tendon, palpation of tendon for pain or defects, evaluating the tendons flexibility, and manual strength test. They may ask you to move the joints near your injured or inflamed tendon. You may experience pain when your provider moves or presses your tendon. Your tendon may also be swollen or warm. Your provider will also test your range of motion around your area of pain. Sometimes the areas around your joints may also feel stiff or weak.
Your healthcare provider may also use tests including:
- Arthrocentesis (joint aspirations).
- Magnetic resonance imaging (MRI).
- Ultrasound (sonography).
How are tendon problems treated?
Healthcare providers treat tendon problems in different ways, depending on the condition:
- Strains: Rest, ice, compression and elevation (RICE), followed by exercises, can offer relief. Strains rarely need surgery.
- Tears: Rest, anti-inflammatory medications ease discomfort as a tendon tear heals. You may need surgery to repair a tear.
- Tendinitis: Tendinitis can improve with rest, ice or heat, anti-inflammatory medications, splints and exercise. The condition sometimes requires surgery, followed by physical therapy.
- Tendinosis: Providers may advise rest, ice or heat, braces, exercise and physical therapy. You should avoid anti-inflammatory medications or steroid injections, which can slow down collagen repair.
- Tenosynovitis: Rest, splints and anti-inflammatory medications can treat tenosynovitis, but some people need surgery.
How can I keep my tendons healthy?
To help reduce your risk of tendon conditions:
- Balance cardio exercise, strength training and flexibility: Keeping your body moving in a variety of ways can prevent you from overtaxing your tendons.
- Listen to your body: Taking it easy when you’re tired or stressed can lessen your risk of injuries.
- Stop an activity if pain occurs: If you experience any pain during an activity, stop doing it and try again later to see if the pain reoccurs.
- Stretch after exercise: Stretching your muscles when they’re more pliable after exercise, and never to the point of pain, can help prevent tendon injury.
- Warm up before you exercise: Doing some light aerobic activities or running in place before more intense exercise increases blood flow rates and loosens up tendons.
- Wear proper athletic shoes: Making sure your shoes fit well and are designed for the sport you’re playing can help keep your body in alignment.
- Work in rest days: Scheduling regular days off can lessen the chances of overstressing your tendons.
Frequently Asked Questions
When should I call a healthcare provider about my tendons?
Talk to a healthcare provider right away if you experience:
- Joint or muscle pain that happens suddenly.
- Pain that gets worse.
- Inability to lift or move part of your body as you usually do.
Without proper treatment, continued overuse of your tendons can lead to tendinosis. If you notice ongoing discomfort, talk to a provider about how to protect your tendons.
A note from Cleveland Clinic
Tendons connect your muscles to your bones. They let your bones move as your muscles tighten and relax. Conditions that affect your tendons include strains, tendinitis and tears, including rotator cuff tears and biceps tendon injuries. You can help keep your tendons healthy by monitoring your exercise habits and not pushing yourself past the point of pain. Be sure to see your healthcare provider if you have pain that doesn’t go away or comes back.
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