Shoulder, Hip, and Knee Anatomy

The shoulder, hip, and knee are the three large appendicular synovial joints most often imaged, and each has a regional anatomy that imaging must depict in detail: the glenohumeral joint with its labrum and rotator cuff, the hip with its acetabular labrum and capsulolabral complex, and the knee with its menisci, cruciate and collateral ligaments. This topic gathers the normal imaging anatomy of these regions.

Definition

Shoulder, hip, and knee anatomy, in imaging terms, is the regional description of the normal osseous and soft-tissue components of these three large appendicular synovial joints and their characteristic appearances across MRI, radiography, CT, and ultrasound.

Scope

The topic covers the principal anatomical components of the shoulder (glenohumeral and acromioclavicular joints, glenoid labrum, rotator cuff), the hip (acetabulum, femoral head, labrum, capsulolabral complex), and the knee (femorotibial and patellofemoral compartments, menisci and meniscal roots, cruciate and collateral ligaments) as they appear on imaging. It is an anatomical reference and does not provide criteria for diagnosing injury of these joints.

Core questions

• What are the normal components of the shoulder, hip, and knee, and how does each appear on imaging?
• How are the labrum, menisci, and intra-articular ligaments depicted on MRI?
• Why are dedicated sequences and planes used for each of these joints?

Key concepts

• Glenohumeral joint, glenoid labrum, and rotator cuff
• Acetabular labrum and capsulolabral complex
• Medial and lateral menisci and meniscal roots
• Anterior and posterior cruciate ligaments
• Collateral ligaments
• Patellofemoral and femorotibial compartments
• Joint-specific imaging planes and sequences

Mechanisms

Each of these joints couples a bony articulation with specialised soft tissues that MRI resolves by signal. In the shoulder, the fibrocartilaginous glenoid labrum and the tendons of the rotator cuff are evaluated on oblique planes aligned to the glenoid and supraspinatus. In the hip, the acetabular labrum forms part of a capsulolabral complex whose normal anatomy and MRI features are well characterised (Flores et al., 2024). In the knee, the menisci appear as low-signal fibrocartilage wedges anchored by meniscal roots (Aydıngöz et al., 2023), while the cruciate and collateral ligaments and the layered anterior structures are assessed on dedicated planes (Flores et al., 2018). Plane and sequence selection follows the regional anatomy described in systematic and atlas references (Standring, 2020; Manaster et al., 2013).

Clinical relevance

A detailed grasp of the normal imaging anatomy of the shoulder, hip, and knee underlies the recognition of departures from normal in orthopaedics, sports medicine, and radiology, including labral, meniscal, and ligamentous structures. This entry describes normal regional anatomy for reference and is not a basis for diagnosis or treatment.

Evidence & guidelines

Normal regional imaging anatomy of these joints is documented in modality-specific pictorial reviews (Flores et al., 2024; Flores et al., 2018; Aydıngöz et al., 2023) and in cross-sectional imaging atlases and systematic anatomy references (Manaster et al., 2013; Standring, 2020).

History

The gross anatomy of the shoulder, hip, and knee has been described since classical anatomy, but their internal soft-tissue structures became directly visible only with cross-sectional imaging. MRI in particular transformed assessment of the labrum, menisci, and intra-articular ligaments, and successive pictorial reviews have refined the description of normal regional anatomy and its variants (Flores et al., 2024; Aydıngöz et al., 2023).

Seminal works

• flores-2024-hip
• aydingoz-2023-meniscus
• flores-2018-knee

Frequently asked questions

Why is MRI the main modality for the shoulder, hip, and knee?

These joints depend on soft-tissue structures such as the labrum, menisci, cruciate ligaments, and rotator cuff that radiography cannot directly show; MRI resolves them by their signal characteristics, which is why it is central to imaging these regions.

What are meniscal roots?

Meniscal roots are the attachments that anchor each meniscus to the tibial plateau; they are part of normal knee anatomy, and recognising their normal appearance on MRI is important when assessing the menisci.