The intertubercular groove, also known as the bicipital groove, is a narrow, elongated depression found on the humerus, the long bone of the upper arm. This structure plays a significant role in the biomechanics of the shoulder joint and arm movement. It functions as a protective channel for soft tissues. This article details the groove’s placement, defining structures, hosted soft tissues, and associated painful conditions.
Locating the Intertubercular Groove
The intertubercular groove is situated on the proximal end of the humerus, closest to the shoulder joint. It runs vertically down the anterior surface of the bone. This depression is positioned precisely between two prominent bony projections: the greater tubercle (located laterally) and the lesser tubercle (located medially).
The groove begins just below the head of the humerus and extends down the shaft of the bone. It serves as a natural division, separating the two tubercles, which are attachment sites for several rotator cuff muscles.
The Crests and Floor of the Groove
The structure of the intertubercular groove is defined by two elevated ridges, or crests, that form its walls. The lateral wall is created by the crest of the greater tubercle, also called the lateral lip. The medial wall is formed by the crest of the lesser tubercle, known as the medial lip.
The space between these two lips is the floor of the groove, which is a smooth, concave surface. These crests descend from their respective tubercles, gradually becoming less pronounced as they move down the humerus. This structural arrangement creates a protective channel that is typically deep and narrow at its upper end.
Tendons and Muscles of Attachment
The primary structure that utilizes the intertubercular groove is the long head tendon of the biceps brachii muscle. This tendon runs through the groove, using it as a pathway to reach its attachment point on the scapula (shoulder blade). The tendon’s stability within this bony channel is maintained by the transverse humeral ligament. This ligament is a band of tissue that bridges the gap between the two crests, effectively converting the groove into a tunnel.
The crests and the floor of the groove also serve as attachment points for three large muscles that contribute to arm movement. The pectoralis major muscle inserts onto the lateral lip of the groove, while the teres major muscle attaches to the medial lip. Sandwiched between these two “major” muscles, the latissimus dorsi muscle inserts directly onto the floor of the intertubercular groove.
Injuries and Associated Pain
The soft tissues passing through the groove are susceptible to painful conditions, most commonly biceps tendinitis. This occurs when the long head tendon of the biceps brachii muscle becomes inflamed as it repeatedly slides within the bony channel. Patients often experience pain and tenderness directly over the front of the shoulder, which typically worsens with overhead or repetitive arm activities.
Another issue is biceps tendon instability, which involves the long head of the biceps tendon moving out of its designated groove. This subluxation or dislocation often results from a tear or injury to the transverse humeral ligament, which normally holds the tendon in place. Instability can cause a noticeable snapping or clicking sensation in the anterior shoulder, indicating the tendon is moving abnormally across the bone.