diff --git a/lms/static/sass/discussion/views/_thread.scss b/lms/static/sass/discussion/views/_thread.scss
index b2cce08d1e..58cc8aa74f 100644
--- a/lms/static/sass/discussion/views/_thread.scss
+++ b/lms/static/sass/discussion/views/_thread.scss
@@ -134,6 +134,10 @@ body.discussion {
         border-radius: 3px;
       }
     }
+
+    img {
+      max-width: 100%;
+    }
   }
 
   .discussion-response .response-body {