Often caused by a paralabral cyst originating from an inferior labral tear (SLAP testing was negative remember), QSS may also result from fibrous bands of soft tissue or tumors/haematomas. The Quadrilateral Space houses the Axillary nerve and Posterior Circumflex Humeral artery and as noted in the image above, is bounded superiorly by the Teres Minor, inferiorly by the Teres Major, medially by the long head of the Tricep and laterally by the humeral shaft. Pain with encroachment of this space is often characterized as a dull, ache and also provoked by local palpation.
This condition is often confused for internal or external impingement, and often is diagnosed ONLY after found incidentally upon MRI (Paralabral cyst + Teres minor atrophy and rarely involving the Deltoid) or MR arthrogram (Labral lesion).
Since this condition is often overlooked upon initial examination, it is important for the clinician to keep this differential in mind when when an athlete participating in contact sports complains of dull/achy lateral shoulder pain, palpable tenderness posteriorly, external rotation weakness and Teres minor atrophy. Conservative manual therapy may alleviate soft tissue adhesions, but proper diagnosis may also warrant MR investigation and/or orthopaedic consultation. Since appropriate care will increase the chances for full recovery, time away from competition can be minimized to several weeks in simple cases and up to 3-6 months in those requiring surgical intervention.