The Labral Labyrinth: SLAP injuries – Part 1

Epidemiology and Risk Factors 

SLAP injuries are fairly uncommon and account for only 5% of all shoulder injuries. It is usually found in the dominant shoulder of overhead athletes, and glenohumeral internal rotation deficit (GIRD) is a risk factor⁽²⁾. Contact sports, such as rugby, increase the risk of injury due to certain factors, including the shoulder position when diving for a try, falling on the field, and playing in front-row positions where the shoulder is most vulnerable^(5,6).

“The accurate diagnosis and management of SLAP tears demand a nuanced approach.”

Mechanism of Injury

The “peel-back mechanism” occurs when the long head of the biceps pulls on the superior glenoid labrum with shoulder and elbow movements. When the shoulder is in the extreme ranges of abduction and external rotation, there is a torsional force of the biceps-labral anchor. This can lead to superior-posterior labral detachment. A sudden forceful traction from above the head and loaded activity (such as a fall on an outstretched arm) where the bicep is tensed or bracing, can also cause an avulsion of the labrum to its superior attachment site. Contributing factors may involve the tightness of the posterior band of the inferior glenohumeral ligament (IGHL), which causes a posterior shift in the glenohumeral contact point and elevates shear forces on the superior labrum. SLAP lesions further increase strain on the anterior band of the IGHL, thereby compromising shoulder stability⁽²⁾.

Classification

In the 1990s, clinicians at the Southern California Orthopedic Institute defined four types of SLAP tears based on arthroscopic investigation⁽⁷⁾. More recently, in 2023, South African clinicians added six additional classifications (see table 1). However, there is wide variability in the inter- and intra-rater classification of SLAP tears⁽⁸⁾.

Table 1: Classification of SLAP injuries⁽⁸⁾

The incidence of SLAP lesions varies across the evidence, with type I accounting for approximately 9.5–21%, type II being the most common at 41–55%, type III ranging from 6% to 33%, and type IV reported in 3–15% of cases. Clinicians observe Type II SLAP lesions most frequently during arthroscopy, and a comparable prevalence is typically seen on MRI⁽⁹⁾.

Presentation

The main complaint with a SLAP lesion is vague, deep shoulder pain, with some patients describing a memorable popping sensation during a past overhead activity. They may point to an area of deep pain (anterior or posterior) somewhere between the acromion and the coracoid process⁽²⁾. There can be a delay between the initial injury and the onset of symptoms. Pain is generally intermittent and is felt during overhead activity, lying on the affected arm (not necessarily at night), and with quick whipping movements, such as throwing a cricket ball or hitting a squash ball. Furthermore, athletes may present with clicking and locking (with or without pain), loss of scapular and rotator cuff strength and stability, and a decrease in internal shoulder rotation. This often leads to reduced performance in muscular power and throwing speed, accompanied by diminished precision and control, particularly impacting athletes who rely heavily on overhead or throwing motions, such as baseball pitchers, tennis players, and swimmers.

“A thorough clinical examination should be tied to a subjective history.”

Diagnosis

A thorough clinical examination should be tied to a subjective history. While no single provocative test is definitive for diagnosing SLAP tears, a combination of tests can be useful in making a diagnosis. The history and patient presentation should give a clinician a high index of suspicion, and they should use clinical tests to add confidence to their diagnosis⁽¹⁰⁾.

Clinicians should assess scapular alignment and any signs of muscle wasting, particularly around the shoulder girdle. Palpation over the bicipital groove may provoke tenderness, suggesting involvement of the long head of the biceps tendon, but is not diagnostic of a SLAP tear. The biceps tendon may be a secondary pathology to the SLAP injury. During assessment of shoulder range of motion (ROM), a clicking or popping sensation may be reproduced during overhead movements, but this is not diagnostic of a SLAP tear as a stand-alone finding⁽¹¹⁾. Clinicians should note the changes in internal rotation range and total rotational range and compare them to those on the opposite side. Up to 85% of patients with SLAP lesions demonstrate apprehension during testing⁽¹²⁾.

Neurovascular and Special Testing 

Neurological examination may reveal supraspinatus and infraspinatus atrophy, potentially indicating suprascapular nerve involvement. There are over 26 tests in the literature that clinicians use to diagnose or rule out SLAP tears. However, there is no single maneuver that can accurately diagnose SLAP lesions (see table 2)⁽¹⁴⁾.

Table 2: SLAP Special tests^(12-16)

Standard radiographs are often unremarkable in suspected SLAP lesions. MRI, complemented by an MR arthrogram, is the imaging gold standard when clinical suspicion remains high, with a sensitivity for SLAP lesions of around 50%. However, specificity reaches up to 90% and is enhanced with the use of an arthrogram. The presence of a paralabral ganglion cyst, particularly in the spinoglenoid notch, is highly suggestive of a labral tear⁽¹⁷⁾.

The accurate diagnosis and management of SLAP tears demand a nuanced approach. These injuries, often resulting from trauma or repetitive overhead activities, can be elusive, with standard assessments and imaging sometimes failing to detect them, leading to persistent shoulder discomfort. A comprehensive clinical evaluation remains paramount and special tests on their own don’t provide diagnostic accuracy, while combining them improves accuracy marginally⁽¹³⁾. However, even combining tests remains disputed⁽¹⁵⁾. Part two will discuss the management options and provide clinicians with clarity on the best approach to helping athletes recover. 

“The main complaint with a SLAP lesion is vague, deep shoulder pain…”

References

1. Brukner & Khan’s clinical sports medicine (5th ed.). 2017: 342-346.
2. Orthobullets. (n.d.). SLAP lesion. Retrieved May 25, 2025, from www.orthobullets.com/shoulder-and-elbow/3053/slap-lesion?section=bullets
3. Radiopaedia.org. (n.d.). Buford complex. Retrieved May 25, 2025, from radiopaedia.org/articles/buford-complex.
4. J Shoulder Elbow Surg.1994, 3(6), 379–385.
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14. Am J Sports Med. 2006 Feb; 34(2).
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16. Am J Sports Med. 2017 Mar;45(4):775-781
17. Open Orthop J. 2018. 12: 314.