Musculoskeletal injuries such as a torn or degraded cartilage can be a debilitating condition if left unaddressed. Cartilage is the soft tissue padding which is present between all joint and bones and acts like a shock absorber. Understandably cartilage experiences a lot of wear, tear and damage over time. The cartilage is essentially avascular (has no blood or nerve supply) and is therefore quite a difficult area to heal. Long term therapy is essential in ensuring healthy repair so that further complications are not experienced in the future.
In regards to acupuncture many people find that this modality gives good results, this is because acupuncture is able to relieve and move the inflammation away from the site of damage and improve the circulation to the area, thereby improving the natural healing abilities. However, having an acupuncture session while the shoulder is experiencing acute exacerbations of pain is not recommended. I suggest waiting until the inflammation settles down as acupuncture may exacerbate the immediate symptoms of pain (although it would still be of benefit).