<s>[INST] Hello doctor, I am a 21-year-old female 5'2" in height and 70kg weight. I have injured my left shoulder three times in horse riding accidents over the years but never got it checked. I then recently carried a heavy bag with the arm hanging down for roughly 10 minutes, four times over a few hours. The next day I had severe general pain in the back of the shoulder or scapular but had full and no more pain in moving shoulder. General pain increased after use of the arm though. Pain gets worse at night. I also have a tingling sensation down the back of the tricep, from the armpit to elbow and one spot roughly above the radial nerve when using the arm. X-rays have been taken. I have an appointment with my doctor tomorrow, but I have copies of the x-rays. They appear to show an AC separation with posterior displacement of clavicle. Can you tell me if I may be correct from the scans? And, is it possible that I had previously injured the AC joint, but the bag carrying tore the ligaments? [/INST] Hello. I will answer your last question first, the answer is no. You can strain your ligaments but cannot tear them by carrying heavy loads unless you have strained a poorly healed torn ligament. Unlikely if you had no deformity to start within the shoulder and no immediate pain after carrying loads. The issue of posterior displacement of the A/C joint can only be confirmed on an MRI or a CT scan as the plane of the movement is challenging to assess on the X-ray films. Tingling sensation at the back of the arm points towards a neck problem while night time symptoms look to shoulder pathology. You should have the answers following the review by an orthopedic surgeon. You could upload your films for better treatment. </s>