The most important tendons
The Achilles tendon (lat. Tendo calcaneus) is the strongest tendon in the human body. It can withstand loads of up to 800kg.
Its length is between 20 and 25 cm and it connects the three-headed calf muscle (Musculus triceps surae) with the heel. This enables the foot to bend towards the sole of the foot (plantar flexion) and to lift the inner edge of the foot (supination). These movements are fundamental to walking and running.
The Achilles tendon reflex is also important in this context, which can be checked by moderately striking the tendon with a reflex hammer. If the reflex can be triggered, the foot should bend towards the sole of the foot. This can be used to check whether the spinal cord is functioning properly at the level of the sacral region (segments S1-S2).
In athletes, the Achilles tendon is more frequently affected by injuries. Should the tendon tear completely (Achilles tendon rupture), this usually manifests itself in a loud, whip-like bang. In young people, surgery is usually indicated, while older people are sometimes treated conservatively (immobilization, painkillers).
Excessive strain on the Achilles tendon is also found in cases of obesity and orthopedic foot malpositions (e.g. pigeon-toed foot). Historical background: The Achilles tendon got its name from Greek mythology. Achilles was there a mortal son of a human father and the sea nymph Thetis.She dipped her son into a river, the Styx, to make him invulnerable.
She held him by the heel, so that the heel could not be wetted by the water of the river. This so-called Achilles’ heel remained his only vulnerable spot. The quadriceps tendon connects the large thigh extensor muscle (M. quadriceps femoris) with the kneecap (patella).
It therefore serves to transfer force from the thigh to the knee and to fix the kneecap, which is embedded in the quadriceps tendon and held in its natural position. The quadriceps tendon is then continued in the lower knee area by the patellar tendon, which ultimately transmits the force to the lower leg. Sports activities involving running, jumping and frequent abrupt braking can lead to inflammation of the quadriceps tendon (tendinitis).
Complete rupture of the quadriceps tendon can also be triggered by strong abrupt braking movements. As a rule, however, the tendon has already been damaged. The injury is usually treated surgically and results in a long-term immobilization in a plaster cast followed by intensive rehabilitation training.
The patellar tendon (lat. Ligamentum patellae) is a continuation of the tendon of the large thigh extensor muscle (Musculus quadriceps femoris) and runs from the lower edge of the patella to its point of attachment on the front tibia. The tendon is about 7cm long and 5-6mm thick.
Its main task is to transmit force from the thigh to the lower leg so that a powerful extension of the leg is possible. It also gives stability to the knee joint and fixes the kneecap in its proper position. The patellar tendon is frequently affected by injuries in various sports.
A complete tear is rare. Instead, overloading the tendon causes tiny tears (micro tears) in the tissue. This usually manifests itself as pressure pain in the area of the lower patella, as well as pain when the affected leg is extended.
This clinical picture is also known as patellar tip syndrome. Treatment is usually carried out by reducing the load and administering anti-inflammatory medication. The patellar tendon can also be used to check the functionality of the spinal cord, namely by triggering the patellar tendon reflex.
To do this, the tendon is tapped with a reflex hammer while the knee is bent. If the reflex can be triggered, the lower leg should be propelled forward. The spinal cord segments examined in this procedure are located in the lumbar spine area (segments L2-L4).
The biceps muscle of the upper arm (Musculus biceps brachii) has some special features. It has a large and a small head, each with its own tendon in the shoulder area. The common base of both heads lies in the large biceps tendon in the crook of the elbow, where it starts at a roughening on the radius of the radius.
This distal biceps tendon is about 22mm long and 7mm thick. Its main task is to transfer force from the upper arm to the forearm and thus to bend the elbow joint (flexion). In addition, it serves the outward rotation of the forearm (supination).
To check the associated biceps tendon reflex, this region can also be tapped with a reflex hammer after the examiner’s thumb is placed on the tendon. If the reflex is properly triggered, the biceps muscle contracts, causing the elbow joint to flex. The biceps tendon reflex characterizes the functionality of the spinal cord segments C5-C6 in the lower neck region.
Besides the distal biceps tendon, the two original tendons of the heads of the biceps muscle are also important. The tendon of the large head, the proximal (near the trunk) long tendon, plays a particularly important role here. Its primary purpose is to rotate the shoulder joint inwards and spread it out.
The tendon runs over the head of the humerus in its own tendon sheath under the acromion and is often affected by degenerative changes, especially in elderly people. With increasing age, wear and tear and calcification occur, which is why this tendon then causes pain or can even tear. The long biceps tendon is also often damaged by overloading during sports that place heavy demands on the shoulder (e.g. baseball).
The tendon of the small head of the biceps muscle is less frequently affected by injuries. Its main purpose is to bring the upper arm closer to the body (adduction). If the long biceps tendon fails, e.g. due to rupture, the short biceps tendon can take over most of the tasks, resulting in a loss of strength of only about 15%.This is also the reason why in many cases a tear of the long proximal biceps tendon is not reversed surgically, but the tendon is merely fixed to the upper arm in its defective position.
The triceps tendon connects the triceps muscle on the upper arm with the elbow. The tendon radiates with some fibers into the joint capsule of the elbow joint and serves to stabilize it. Under the triceps tendon there is a bursa, which prevents excessive friction between the tendon and the bone.
The main function of the triceps tendon is the transmission of force between the upper arm and ulna, whereby it mediates the extension of the elbow joint. This function can be checked by triggering the triceps tendon reflex. For this purpose, the tendon directly above the elbow (olecranon) is tapped with the reflex hammer.
The reflex, which can actually be triggered, manifests itself by an extension in the elbow joint. The spinal cord segments C7 and C8 in the lower neck area are checked. Since the triceps runs very superficially along the arm, it can easily be injured in accidents.
However, a tear of the triceps tendon is very rare and is even the rarest tendon injury in orthopedics. Normally, such a tear only occurs in the case of a previously damaged tendon or a fall on the arm, in which case the tendon usually tears off in a bony way, i.e. together with a piece of the elbow. The rupture is usually treated surgically.
The rotator cuff is a muscle-tendon plate, which is formed by the tendons of the four shoulder rotators and surrounds the shoulder joint. The muscles involved are the supra- and infraspinature muscles, the subscapularis muscle and the minor teres muscle. These muscles are responsible for the inward and outward rotation of the shoulder joint and stabilize it in position by means of the formed tendon plate.
This is important because the shoulder joint has very little ligament-based security and is therefore dependent on increased muscular fixation. Injuries to the shoulder can result in tendon ruptures in the area of the rotator cuff (rotator cuff rupture). Since the tendons in the shoulder area are subject to heavy strain, signs of wear and tear are also common.
The therapy of the injuries depends on their extent. If the rotator cuff tears completely, surgery must be performed in any case.
