{"schemaVersion":1,"id":"en-anatomy-shoulder-joint","type":"anatomy","pillar":"body","locale":"en","translationGroupId":"anatomy-shoulder-joint","slugPath":"body/joints/shoulder","title":"The shoulder","shortTitle":"Shoulder","summary":"The most mobile joint in the body, and the one that holds least by its shape. A wide head resting on a shallow socket, retained by soft tissue.","level":"intermediate","estimatedMinutes":8,"synonyms":["shoulder","glenohumeral joint","glenoid labrum","labrum","joint capsule","acromioclavicular"],"blocks":[{"id":"b1","type":"heading","level":2,"text":"The word shoulder covers several joints","anchor":"the-word-shoulder-covers-several-joints"},{"id":"b2","type":"paragraph","content":[{"kind":"text","value":"Saying \"the shoulder\" really names a set. Four linkages take part, and one arm movement brings them all into play."}]},{"id":"b3","type":"list","ordered":false,"items":[[{"kind":"text","value":"The "},{"kind":"strong","value":"glenohumeral"},{"kind":"text","value":" joint links the head of the humerus to the glenoid cavity of the shoulder blade. That is the one described here."}],[{"kind":"text","value":"The "},{"kind":"strong","value":"acromioclavicular"},{"kind":"text","value":" joint links the end of the collarbone to the acromion."}],[{"kind":"text","value":"The "},{"kind":"strong","value":"sternoclavicular"},{"kind":"text","value":" joint attaches the collarbone to the breastbone, the only point where the upper limb touches the skeleton of the trunk."}],[{"kind":"text","value":"The "},{"kind":"strong","value":"scapulothoracic"},{"kind":"text","value":" gliding is not a joint in the strict sense: the shoulder blade slides on the ribs, with no articular surface."}]]},{"id":"b4","type":"paragraph","content":[{"kind":"text","value":"That last one supplies roughly a third of the range of arm elevation, driven by "},{"kind":"link","value":"serratus anterior","href":"/en/body/muscles/serratus-anterior","external":false},{"kind":"text","value":" and the "},{"kind":"link","value":"trapezius","href":"/en/body/muscles/trapezius","external":false},{"kind":"text","value":"."}]},{"id":"b5","type":"heading","level":2,"text":"A socket too small for its head","anchor":"a-socket-too-small-for-its-head"},{"id":"b6","type":"definition","term":"Glenoid cavity","definition":"The hollow articular surface of the shoulder blade that receives the head of the humerus. It is shallow and markedly smaller than the head it receives.","alsoKnownAs":["glenoid"]},{"id":"b7","type":"paragraph","content":[{"kind":"text","value":"The contrast with the "},{"kind":"link","value":"hip","href":"/en/body/joints/hip","external":false},{"kind":"text","value":" is striking. There, a sphere set deep into a cup. Here, a wide head resting against an almost flat surface, of which it covers only a fraction at a time."}]},{"id":"b8","type":"paragraph","content":[{"kind":"text","value":"This arrangement gives the shoulder the greatest range in the body. It also gives it its dependence on everything that is not bone."}]},{"id":"b9","type":"heading","level":2,"text":"The labrum and the capsule","anchor":"the-labrum-and-the-capsule"},{"id":"b10","type":"paragraph","content":[{"kind":"text","value":"A ring of fibrocartilage, the glenoid labrum, borders the cavity. It deepens the rim and increases the contact area, without changing the essential point: the retention stays modest."}]},{"id":"b11","type":"paragraph","content":[{"kind":"text","value":"The joint capsule wraps the whole. It is loose — it has to allow the range through — and three thickenings reinforce it in front: the superior, middle and inferior glenohumeral ligaments. The coracohumeral ligament completes the arrangement from above."}]},{"id":"b12","type":"evidence","level":"established","statement":"The stability of the glenohumeral joint rests more on soft tissue than on the shape of the bony surfaces.","detail":"Descriptive anatomy and kinesiology describe it the same way: the cavity is shallow, the labrum adds only a limited amount, and the retention comes from the capsule, the ligaments and above all the [rotator cuff](/en/body/muscles/rotator-cuff). The relative contribution of each element varies with arm angle and with the measurement method.","referenceIds":["standring2020","neumann2016"]},{"id":"b13","type":"heading","level":2,"text":"What this implies","anchor":"what-this-implies"},{"id":"b14","type":"comparison","title":"Two joints, two trade-offs","columns":["Criterion","Shoulder","Hip"],"rows":[{"label":"Socket depth","cells":["Shallow","Deep"]},{"label":"Range","cells":["The greatest in the body","More limited"]},{"label":"Source of stability","cells":["Soft tissue and muscle","Bone shape and ligaments"]},{"label":"Cost of holding","cells":["Muscular, continuous","Ligamentous, cheap when standing"]}]},{"id":"b15","type":"paragraph","content":[{"kind":"text","value":"The practical consequence is that the shoulder depends on muscles working continuously. The rotator cuff keeps the humeral head centred while the "},{"kind":"link","value":"deltoid","href":"/en/body/muscles/deltoids","external":false},{"kind":"text","value":" moves the arm. That is no side role: without that centring, the movement does not proceed normally."}]},{"id":"b16","type":"evidence","level":"probable","statement":"Shoulder characteristics differ in people who regularly do resistance training.","detail":"The study covers a population of recreational lifters and describes differences in range and in muscle characteristics. It is an observation on a given group: it establishes no cause and effect and supports no conclusion about any particular person.","referenceIds":["kolber2009"]},{"id":"b17","type":"heading","level":2,"text":"Seeing the shoulder","anchor":"seeing-the-shoulder"},{"id":"b18","type":"scene3d","sceneId":"articulations","title":"The shoulder, bones and joint tissues","intro":"The scene shows the shoulder blade, the collarbone and the upper humerus, with the capsule, the glenoid labrum and the glenohumeral ligaments highlighted. Without the 3D, the idea fits in one sentence: a large head resting against a small socket, held by a supple wrapping and by the muscles around it.","initialStepId":"epaule","accessibility":{"textAlternative":"A three-dimensional model of four joints from the left side of the body, presented one after another on a paper background. The shoulder shows the shoulder blade, collarbone and upper humerus in bone tones, with the joint capsule, the glenoid labrum and the glenohumeral ligaments in olive grey. The hip shows the hip bone and femur, the capsule wrapping the neck, the acetabular labrum and the three ligaments wound around it. The knee shows the femur, tibia, fibula and kneecap, with the two menisci resting on the tibial plateau, the cruciate ligaments at the centre and the collaterals on either side. The lumbar spine, seen from the side, shows the five vertebrae and the sacrum separated by five discs, with the longitudinal ligaments running in front of and behind the vertebral bodies. The joint tissues are highlighted at each step, the bones staying in the background.","structures":[{"label":"Glenoid labrum","description":"A fibrocartilaginous rim fixed around the edge of the glenoid cavity. It deepens the socket and increases the contact area with the head of the humerus, whose diameter far exceeds that of the cavity.","href":"/en/body/joints/shoulder"},{"label":"Ligaments of the hip","description":"Three bands wound around the capsule — iliofemoral, pubofemoral, ischiofemoral. They tighten as the hip extends, which allows standing without continuous muscular effort.","href":"/en/body/joints/hip"},{"label":"Cruciate ligaments","description":"Two ligaments stretched across the centre of the knee, crossing one in front of the other. They limit the tibia sliding under the femur — forwards for the anterior, backwards for the posterior.","href":"/en/body/joints/knee"},{"label":"Intervertebral discs","description":"Five discs separate the lumbar vertebrae and the sacrum. Each pairs a tough fibrous ring with a more deformable core, which spreads load and allows slight movement between two neighbouring vertebrae.","href":"/en/body/joints/lumbar-spine"},{"label":"Ligaments of the elbow","description":"Two collateral ligaments hold the elbow from the sides, and a ring encircles the head of the radius so it can pivot without leaving its place. The elbow thus combines a hinge and a pivot.","href":"/en/body/joints/elbow"},{"label":"Lateral ligaments of the ankle","description":"Three slender bands link the fibula to the talus and the heel bone. They are markedly thinner than their medial counterparts, which is why the ankle is more easily forced inwards.","href":"/en/body/joints/ankle"}],"steps":[{"id":"epaule","title":"The shoulder","body":"The head of the humerus is far wider than the socket that receives it. The glenoid labrum deepens the rim, the capsule wraps the whole, and three glenohumeral ligaments reinforce it in front. That is the price of mobility: little bone to hold, a great deal of soft tissue."},{"id":"hanche","title":"The hip","body":"Unlike the shoulder, the femoral head sits deep in the socket, which the acetabular labrum extends further. The three ligaments wind around the neck and tighten in extension: standing, they carry part of the work the muscles no longer have to supply."},{"id":"genou","title":"The knee","body":"Two poorly matched surfaces — the rounded condyles of the femur on an almost flat tibial plateau. The menisci fill the gap, the cruciates hold the tibia front to back, the collaterals hold it side to side. Remove any one of these parts and the load shifts onto the others."},{"id":"rachis-lombaire","title":"The lumbar spine","body":"Five vertebrae, five discs, and a set of ligaments running the whole height. Each level moves only a few degrees; it is their sum that gives the trunk its range. The longitudinal ligaments limit flexion and extension, the ligamenta flava close the back of the canal."},{"id":"coude","title":"The elbow","body":"The elbow does two things inside one capsule. The humerus and ulna form a hinge that flexes and extends in a single plane; the head of the radius pivots in place inside a ligamentous ring, which turns the palm over. The two collateral ligaments hold it all from the sides."},{"id":"cheville","title":"The ankle","body":"The talus is wedged between the two malleoli like a tenon in a mortise. On the inner side, a thick fan-shaped ligament; on the outer side, three markedly thinner bands. That asymmetry is no detail: it explains which way the ankle most often gives."}],"license":"Z-Anatomy et BodyParts3D — CC-BY-SA 4.0"}},{"id":"b19","type":"heading","level":2,"text":"What the model simplifies","anchor":"what-the-model-simplifies"},{"id":"b20","type":"callout","tone":"limit","title":"What the image is missing","content":[[{"kind":"text","value":"The cartilage and the bursae are not represented. The subacromial bursa in particular occupies the space between the rotator cuff and the acromion, and that space sits at the heart of many discussions about the shoulder."}],[{"kind":"text","value":"The gliding of the shoulder blade on the ribcage does not appear as a joint, since strictly it is not one. It nonetheless supplies a large share of arm range, and ignoring it would give an incomplete picture of the movement."}]]},{"id":"b21","type":"heading","level":2,"text":"Related structures","anchor":"related-structures"},{"id":"b22","type":"paragraph","content":[{"kind":"text","value":"The shoulder is stabilised by the "},{"kind":"link","value":"rotator cuff","href":"/en/body/muscles/rotator-cuff","external":false},{"kind":"text","value":" and moved by the "},{"kind":"link","value":"deltoid","href":"/en/body/muscles/deltoids","external":false},{"kind":"text","value":", "},{"kind":"link","value":"pectoralis major","href":"/en/body/muscles/pectoralis-major","external":false},{"kind":"text","value":" and the "},{"kind":"link","value":"latissimus dorsi","href":"/en/body/muscles/latissimus-dorsi","external":false},{"kind":"text","value":". The orientation of the socket depends on "},{"kind":"link","value":"serratus anterior","href":"/en/body/muscles/serratus-anterior","external":false},{"kind":"text","value":" and the "},{"kind":"link","value":"trapezius","href":"/en/body/muscles/trapezius","external":false},{"kind":"text","value":". It works in "},{"kind":"link","value":"vertical pushing","href":"/en/movements/vertical-push","external":false},{"kind":"text","value":" and "},{"kind":"link","value":"pulling","href":"/en/movements/vertical-pull","external":false},{"kind":"text","value":"."}]},{"id":"b23","type":"heading","level":2,"text":"Sources","anchor":"sources"},{"id":"b24","type":"sourceList","title":"Main sources","referenceIds":["standring2020","neumann2016","kolber2009"]},{"id":"b25","type":"shapierAction","actionId":"exercises-developpe-epaules","label":"Practise the shoulder press","description":"The shoulder press, a vertical push that loads the deltoid, is practised in Shapier; Body Lab only explains the joint it puts into play.","webTarget":"https://shapier.app/en/exercises/developpe-epaules","appTarget":"shapier://exercises/developpe-epaules"},{"id":"b26","type":"quiz","title":"Check my understanding","questions":[{"id":"q1","prompt":"What mainly retains the head of the humerus in the glenoid cavity ?","choices":[{"id":"q1c1","label":"Soft tissue: the capsule, the ligaments and above all the rotator cuff","correct":true,"explanation":"The cavity is shallow and the labrum adds only a limited amount: stability rests more on soft tissue than on the shape of the bony surfaces."},{"id":"q1c2","label":"The shape of the bony surfaces, as in the hip","correct":false,"explanation":"That is the opposite of the hip arrangement: here a wide head rests against an almost flat surface, of which it covers only a fraction at a time."},{"id":"q1c3","label":"The glenoid labrum, which seats the humeral head","correct":false,"explanation":"The labrum deepens the rim of the cavity and increases the contact area, but the retention it provides stays modest."}]},{"id":"q2","prompt":"Why does scapulothoracic gliding matter in an arm movement ?","choices":[{"id":"q2c1","label":"It supplies roughly a third of the range of arm elevation","correct":true,"explanation":"Driven by serratus anterior and the trapezius, the shoulder blade slides on the ribs, and that share of the range is large, even though it is not depicted as a joint."},{"id":"q2c2","label":"It does not matter, since strictly it is not a joint","correct":false,"explanation":"The shoulder blade does glide without an articular surface, but ignoring it would give an incomplete picture of the movement: it supplies a large share of arm range."},{"id":"q2c3","label":"It attaches the collarbone to the breastbone","correct":false,"explanation":"That is the role of the sternoclavicular joint, the only point where the upper limb touches the skeleton of the trunk."}]},{"id":"q3","prompt":"What can be concluded from the study of shoulders in recreational resistance trainers ?","choices":[{"id":"q3c1","label":"That differences in range and muscle characteristics exist in that group, with no cause and effect established","correct":true,"explanation":"The study describes an observation on a given population: it establishes no causality and supports no conclusion about any particular person."},{"id":"q3c2","label":"That resistance training modifies the shoulder","correct":false,"explanation":"The study observes a given group at a given time: it establishes no cause-and-effect link."},{"id":"q3c3","label":"That these differences explain a shoulder pain","correct":false,"explanation":"An observation on a group supports no conclusion about a particular person; pain belongs to a health professional."}]}]},{"id":"b27","type":"relatedContent","title":"Read next","targetIds":["en-anatomy-rotator-cuff","en-anatomy-hip-joint","en-anatomy-deltoids"]}],"relations":[{"type":"uses-structure","targetId":"en-anatomy-rotator-cuff"},{"type":"produces-movement","targetId":"en-movement-vertical-push"},{"type":"uses-structure","targetId":"en-anatomy-deltoids"},{"type":"next-step","targetId":"en-anatomy-hip-joint"}],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[{"id":"standring2020","authors":"Standring S","year":2020,"title":"Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition","source":"Elsevier","kind":"book","url":"https://shop.elsevier.com/books/grays-anatomy/standring/978-0-7020-7705-0"},{"id":"neumann2016","authors":"Neumann DA","year":2016,"title":"Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition","source":"Elsevier","kind":"book","url":"https://shop.elsevier.com/books/kinesiology-of-the-musculoskeletal-system/neumann/978-0-323-28753-1"},{"id":"kolber2009","authors":"Kolber MJ, Beekhuizen KS, Cheng MS, Hellman MA","year":2009,"title":"Shoulder joint and muscle characteristics in the recreational weight training population","source":"Journal of Strength and Conditioning Research","kind":"journal-article","doi":"10.1519/jsc.0b013e31818eafb4"}],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02","evidenceLevel":"established"},"limitations":["The model shows neither the cartilage nor the bursae, including the subacromial bursa: they nonetheless occupy the space between the cuff and the acromion.","The shoulder is not one joint but a complex: the shoulder blade also glides on the ribcage, and that gliding is not depicted as a joint in its own right.","This page describes an anatomy. Shoulder pain, loss of strength or a shrinking range belong to a health professional: no page can attribute them to a structure."],"seo":{"title":"The shoulder — glenoid cavity, labrum and capsule","description":"Why the shoulder is the most mobile and least fitted joint, what the glenoid labrum does, and what the word shoulder actually covers.","canonicalPath":"/en/body/joints/shoulder","image":"/og/en/anatomy-shoulder-joint.png"},"app":{"offlineEligible":true},"version":1}