Image Interpretation: A small anechoic region is noted deep to the common extensor tendon along the proximal radial collateral ligament, measuring 0.2 x 0.33 x 0.17 cm with underlying cortical irregularity. No hyperemia is noted. The common extensor tendon origin is slightly hypoechoic without thickening or disruption in its fibrillar pattern. These findings are suggestive of a partial thickness tear of the radial collateral ligament with subtle common extensor tendinosis.

Teaching Pearl: The radial collateral ligament (RCL) is one of three components of the lateral collateral ligament (LCL) complex, with the other being the annular ligament (AL) and lateral ulnar collateral ligament (LUCL). Most cases of LCL injury are traumatic, especially after elbow dislocation. Indirect trauma, usually a fall on an outstretched hand can cause radiocapitellar joint posterior subluxation with subsequent damage to the RCL, most commonly at the proximal portion, near the humeral epicondyle. On examination, the patient may experience lateral elbow pain worsened with wrist extension or gripping, a clicking sensation during elbow extension, and occasionally posterolateral elbow instability. Non-surgical treatment is preferred; however, surgical consultation may be warranted if there is persistent joint instability and pain refractory to conservative measures limiting function. Although treatment varies, the basic principles of treatment include relative rest, counterforce bracing, pain management, and a graduated rehabilitation protocol that initially emphasizes isometrics and active range of motion, preferably with pronation and arm overhead while avoiding varus arm positioning. Sources: Graf, D. N., Fritz, B., Bouaicha, S., & Sutter, R. (2021, August). Elbow instability. In Seminars in Musculoskeletal Radiology (Vol. 25, No. 04, pp. 574-579). Thieme Medical Publishers, Inc.. Teixeira PA, Omoumi P, Trudell DJ, Ward SR, Lecocq S, Blum A, Resnick DL. Ultrasound assessment of the lateral collateral ligamentous complex of the elbow: imaging aspects in cadavers and normal volunteers. Eur Radiol. 2011 Jul;21(7):1492-8. doi: 10.1007/s00330-011-2076-8. Epub 2011 Feb 13. PMID: 21318472; PMCID: PMC3101344. Manocha RH, Kusins JR, Johnson JA, King GJ. Optimizing the rehabilitation of elbow lateral collateral ligament injuries: a biomechanical study. J Shoulder Elbow Surg. 2017 Apr;26(4):596-603. doi: 10.1016/j.jse.2016.09.038. Epub 2016 Nov 22. PMID: 27887872.