Overview of all important joints
The shoulder joint (lat. Articulatio humeri) is formed by the uppermost part of the humerus, also called humeral head (lat. Caput humeri), and the socket of the shoulder blade (lat.
Scapula), also called cavitas glenoidalis. It is the most mobile but at the same time the most susceptible joint of the human body. But where does the great mobility of our shoulder joint come from?
The joint surface of the head of humerus is about three to four times larger than the joint surface of the shoulder blade. This pronounced disproportion allows for the great freedom of movement. At the same time, however, stability is reduced because there is no firm, bony guidance.
It is therefore not surprising that about 45% of all dislocations (joint dislocation) fall on the shoulder. From a systematic point of view, the shoulder joint is a ball-and-socket joint. It is named after the almost spherical shape of the head of humerus.
As a typical representative of this joint type, the shoulder has three degrees of freedom, i.e. six possible directions of movement. In addition to the bones involved, ligaments, bursa, joint capsule and muscles are also involved in the formation of the joint.These structures are primarily responsible for the movements of the shoulder. They also have the important task of stabilizing the joint!
For example, the ligament Ligamentum coracoacromiale together with bony parts (lat. Acromion and Processus coracoideus) forms the “acromion” and thus limits upward (cranial) movements. In addition, the strong shoulder muscles secure the joint!
The most important muscle group is the so-called “rotator cuff“. It includes the muscles infraspinatus, supraspinatus, teres minor and suprascapularis. They surround the shoulder from several sides and are mainly responsible for stabilization.
A common injury of the shoulder is the impingement syndrome, also known as painful arch: If the arm is abducted at a lateral angle of between 60 and 120 degrees, sufferers feel great pain. A calcified and thickened tendon of the supraspinatus muscle is responsible. When the arm is lifted, it moves under a bony protrusion and a bursa (lat.
Bursa subacromialis). Finally, the tendon impinges on the arm with increasing movement and is painfully squeezed. The elbow joint (lat.
Articulatio cubiti) is formed by the humerus and the two forearm bones ulna and radius. Within the joint, three partial joints can be distinguished: The upper arm spoke joint (lat. Art.
humeroradialis), the upper arm joint (lat. Art. humeroulnaris) and the proximal ulna spoke joint (Art.
radioulnaris proximalis) (see below). These three individual joints form a functional unit and are enclosed by a common delicate joint capsule. Fan-shaped collateral ligaments, also called collateral ligaments, stabilize the joint and strengthen the capsule.
Furthermore, the ring ligament (lat. Lig. annulare radii) supports the bony guidance in the proximal ulnar radius joint.
In its entirety, the elbow joint allows bending and stretching movements (flexion and extension), as well as rotational movements (pro and supination) of the forearm. In many fine motor activities of the hand, such as turning a screwdriver, unlocking a door lock or guiding food to the mouth, the ability to rotate the forearm is of great importance! 1) Upper arm joint The upper arm spoke joint is formed by the joint roller of the upper arm, the trochlea humeri, and a depression in the ulna, the incisura ulnaris.
From a functional point of view, it belongs to the group of hinge joints and enables flexion and extension of the forearm. 2)Upper arm spoke joint This joint articulates a small cartilaginous surface of the upper arm, also called humerus head or capitulum humeri, with a depression of the spoke, also called fovea articularis radii. Viewed purely from the form, it belongs to the ball and socket joints.
However, a connection of connective tissue between the two forearm bones (Membrana interossea antebrachii) greatly restricts movement! Thus, instead of the usual six directions of movement, there are only four. 3) Proximal ulna-spoked joint The proximal ulna-spoked joint is a swivel joint, more precisely a tenon joint.
On the inside, the strong ring ligament is covered with cartilage and is thus in contact with the joint surfaces of ulna and radius!The term “wrist” colloquially summarizes the proximal radiocarpal joint and the connection between two rows of carpal bones, the mediocarpal joint. A simple distinction is often made between the “proximal” (near the body) and “distal” (far from the body) wrist. The tasks and functions of our hand are also complex, similar to the structure of the two subjoints!
1.) Radiocarpal jointSimplified, the radiocarpal joint connects the forearm bones with the wrist. The distal end of the radius bone, the articular disc (cartilage surface), and three bones of the proximal carpal (scaphoid, lunar bone, triangular bone) form the connection.
If the shape of the joint surfaces is considered, the radiocarpal joint belongs to the group of the ovary joints. Thus it has two axes of motion and four possible directions of motion: Flexion and extension (palmar flexion and dorsal extension), as well as lateral spreading inwards or outwards (radial/ulnar abduction). 2.)
Medio-carpal jointA roughly S-shaped joint gap runs between the proximal (scaphoid, lunate, triangular bone) and distal row of carpal joints (large and small polygonal bone, capitate bone, hooked leg). Two opposing bones each form a single joint. In its entirety it is called the medio-carpal joint.
Functionally it belongs to the hinge joints. Due to numerous ligaments, however, it is severely restricted in its movements.It also interacts with the radiocarpal and intercarpal joints. This is why the physician also calls this joint a “toothed” hinge joint.
Of particular importance are the ligaments of the carpal bones mentioned above. In carpal injuries, for example a scaphoid fracture, they are often affected as well. Elderly people also often suffer from pain caused by wear and tear, for example in the cartilage (discus articularis) of the radio-carpal joint.
With the exception of the thumb, our fingers consist of three small bones each: Basic phalanx (lat. Phalanx proximalis), middle phalanx (lat. Phalanx media) and distal phalanx (lat.
Phalanx distalis). They are in contact with each other through a jointed connection. In every finger except the thumb we find three individual joints.
This enables fine motor and complex movements! Since the thumb has no middle phalanx, it has only two joints. First, the metacarpophalangeal joint connects the metacarpophalangeal bone with the phalanx.
The middle finger joint (Art. interphalangealis proximalis) connects the base and middle finger phalanx and the end finger joint (Art. interphalangealis distalis) connects the middle and end finger phalanx.
Viewed purely in terms of shape, the metacarpophalangeal joint is a ball-and-socket joint. However, the third axis of motion, namely rotation, is strongly restricted by the collateral ligaments. Finally, the fingers in the metacarpophalangeal joint can be bent and stretched and spread to both sides.
In order to simplify the complicated Latin names of the two remaining joints, physicians simply shorten the long names: the middle finger joint becomes PIP, the end finger joint becomes DIP. Both are pure hinge joints with one axis of motion and thus two possible movements (flexion and extension). On the underside of the wrist, the tendons of the long finger flexors each run in a common tendon sheath.
This in turn is attached to the bony finger bones by ring and cruciate ligaments. In addition, the individual finger joints are supported by collateral ligaments (lat. Ligg.
collateralia). Their special feature is that they are relaxed when the fingers are stretched, whereas they are tensioned when they are bent. In the case of plaster casts of the hand, it is therefore absolutely necessary to fix the fingers in a slight flexion!
Otherwise, the collateral ligaments quickly recede and shorten. In the worst case, flexion is no longer possible afterwards. Our knee joint (Art.
genu) consists of two partial joints. On the one hand, the thigh bone (lat. femur) and the tibia (lat.
tibia) form the femorotibial joint. In addition, the patella and thigh articulate in the femoropatellar joint. Both partial joints are surrounded by a common capsule and form a functional unit.
In its entirety, it is a hinge joint with possible flexion, extension, and internal and external rotation. When the knee joint is stretched, the special feature that gives it its name can also be observed: At maximum exercise of the movement, the lower leg turns slightly outwards (“final rotation”). Numerous structures ensure the stability and load-bearing capacity of our knee: cruciate ligaments Within the joint capsule, the anterior (Lig.
cruciatum anterius) and posterior (Lig. cruciatum posterius) cruciate ligaments are stretched. Both ligaments ensure contact between the tibia and thigh and provide stability, especially during rotational movements.
If the cruciate ligaments are injured, patients often experience significant uncertainty or instability in the knee joint. Menisci The name is derived from the crescent-shaped form (Latin meniscus = half moon) of the two cartilage structures. They enlarge the joint surface and thus ensure an even load.
We differentiate between the outer and inner meniscus, whereby the inner meniscus is closely fused with the joint capsule and the inner knee ligament. Accordingly, the inner meniscus is far more frequently affected in injuries! Collateral ligaments On the inner side of the knee joint runs the colloquially known “inner ligament” (lat.
Lig. collaterale tibiale), accordingly one finds the so-called “outer ligament” (lat. Lig.
collaterale fibulare) on the outer side. They prevent our knee from buckling to the side. It is therefore only logical that the collateral ligaments are injured, especially during lateral bending movements.
If both the inner ligament, inner meniscus and anterior cruciate ligament tear, we speak of an “Unhappy Triad”. Our hip joint (lat. Art.
coxae) represents the articulated connection between upper body and legs. On the one hand it enables walking and standing upright, on the other hand it provides stability in the middle of the body! Thigh head, also called femoral head, (lat.Caput femoris) and the acetabulum covered with cartilage (lat.
Acetabulum) form the bony parts. The latter is formed by the fusion of the ilium (lat. Os ilium), ischium (lat.
Os ischii) and pubic bone (Os pubis). The hip joint is a special type of ball joint, namely a nut joint with three axes of motion. Therefore, bending and stretching, inner and outer rotation as well as lateral abduction are possible here.
Characteristic are the strong and massive ligaments, which press the spherical femoral head together with the taut joint capsule firmly into the socket. In this context, the physician often speaks of a “ligament screw”. (iliac-leg ligament, ischium-leg ligament and pubic-leg ligament).
For example, the iliac-iliac ligament has a tensile strength of over 350 kg and is therefore the strongest ligament in the human body! When standing upright, it also prevents the pelvis from tilting backwards without the use of muscle power. Another special feature of the hip joint is the femoral head band.
It contains blood vessels which are extremely important for the supply of the femoral head. It plays a major role in the healing of femoral neck fractures. With increasing age, signs of wear and tear of the hip joint often occur, the so-called coxarthrosis.
In the meantime, experts assume that in Germany about 2% of all 65-74 year olds are affected. Overweight patients without sufficient exercise are particularly at risk. During the course of the disease, pain and immobility in the hip joint increase.
In the worst case an endoprosthesis (“artificial hip”) is the only therapeutic solution. Behind the colloquial term “ankle joint” are the upper (Art. talocruralis) and lower ankle joint (Art.
subtalaris and Art. talocalcaneonavicularis). Many small tarsal bones and ligaments interact very complexly with each other and thus enable, among other things, an upright gait.
Upper ankle jointBoth ends of the lower leg bones far from the body, the tibia and fibula, form the so-called malleolar fork, also known as the ankle fork. It encompasses the joint roll (lat. Trochlea tali) of the ankle bone on both sides and thus forms the upper ankle joint.
The pure hinge joint thus connects the lower leg and the tarsus and allows flexion as well as extension. To stabilize and guide movement, the joint has lateral ligaments (inner and outer ligaments) between the lower leg bone and the tarsus. On the other hand, the tibia and fibula are connected by the syndesomseous ligaments.
Injuries to the upper ankle joint are extremely common. Typically, affected persons bend outwards on uneven ground (suppination trauma). This primarily results in overstretching or even tearing of the outer ligament.
The term “sprain” has become commonly used in many cases. Lower ankle jointInside the lower ankle joint, a distinction is made between a front and rear partial joint. In the anterior lower ankle joint, various tarsal bones (heel bone, scaphoid bone) and the cartilage-covered socket ligament form a socket for the ankle bone (lat.
talus). In addition, the glenoid ligament reinforces the longitudinal arch of the foot. The posterior lower ankle joint consists of the anklebone and the heel bone (lat.
Calcaneus). Between the two chambers of the lower ankle joint runs the ankle-heelbone ligament (lat. Lig.
talocalcaneum interosseum) and thus forms the spatial dividing line. Similar to the upper ankle joint, the range of motion in the joint is limited to one axis of motion: With the ankle fixed from the front, the heel can be turned both inwards (inversion) and outwards (eversion). Ultimately, however, it is difficult to reduce the movements in the foot to individual joints.
This is because almost all components within the foot are coupled to each other, so that movements are usually executed in combination. Colloquially, all joints of the toe bones fall under this term. Their structure is very similar to the finger joints.
Accordingly, each toe, with the exception of the big toe, consists of three small bones: The proximal phalanx, the middle phalanx (lat. Phalanx media) and the distal phalanx (lat. Phalanx distalis).
Between the individual heads of the metatarsal bones and the metatarsophalangeal joints of all toes we find the metatarsophalangeal joints (lat. Art. metatarsophalangea).
The metatarsophalangeal joint (Art. interphalangealis proximalis, PIP) is located between the metatarsal and metatarsophalangeal joints. Like the thumb, the big toe consists only of the base and distal phalanx.
Since it has no middle phalanx, the corresponding middle toe joint is also missing! On all toes, however, the terminal joint (lat. Art.
interphalangealis distalis, DIP) connects the middle/base and terminal phalanx.In some people, the last two bone members of the little toe are fused together. In summary, there are five metatarsophalangeal joints, four metatarsophalangeal joints and five metatarsophalangeal joints. From a functional point of view, the joints between the toe bones belong to the hinge joints.
Through them we can bend and stretch our toes. This ability is an important prerequisite for walking and running. Numerous ligaments, tendons and muscles support the complicated anatomy.
Typical complaints of the toe joints can occur, for example, in the context of foot malpositions. Especially in the clinical picture of the splayfoot, the basic joints of the toes II-IV cause complaints. The typical loss of the transverse arch of the foot causes an increased pressure load on the head of the foot. In addition, the small toe joints are often affected by arthrosis with increasing age.
