by Adrienne Ingram
What is it?
The name suggests that Myositis Ossificans is an inflammatory process of new bone forming inside a muscle. However, it should be taken a little less literally. It has been shown to have little to do with any inflammation, but more to do with new, harder deposits of bony or cartilaginous tissue growing in the muscle. This is usually in response to trauma. As the muscle attempts to repair itself, instead of laying down new muscle cells (fibroblasts), immature bone cells (osteoblasts) are formed instead (Walkzak, Johnson & Howe, 2015). MO most commonly occurs in young athletes playing contact sports.
There are three classifications of MO: Traumatic, Non-traumatic and Neurotic.
What causes it? 
The most common cause of MO is trauma, generally a single contusion (think corky), or otherwise repetitive trauma to an area; in even rare cases can be following a severe muscle tear. Traumatic MO is thought to occur as a complication in around 20% of severe muscle haematomas (corkies) (Torrence, 2011).
The latter two types of MO (non-traumatic and neurotic) can be associated with burns, polio, paraplegia and infections, however are very rare.
What does it feel like?
Symptoms can vary person to person, but pain and limited range of motion are the first signs of MO. These are common symptoms of a number of injuries, but following trauma, MO is suspected if these symptoms last for longer than a usual muscle tear, strain or corky would. You may also be able to feel a small mass or lump in the affected area. It is not likely to be diagnosed as MO until at least 2-4 weeks after the injury, as it takes some for bony calcification to occur, and for the blood pooling from the initial injury to dissipate (Torrence, 2011).
If your physio suspects that you have an MO, they will refer you for a scan (most commonly an ultrasound, with and MRI to follow up if necessary) to confirm.
How do you manage it?
Firstly – RICE! Rest, Ice, Compression and Elevation. It is important to then seek advice from your physiotherapist about immediate management and ongoing rehabilitation.
Conservative management through Physiotherapy is the first line of treatment. Restoring range of motion and strength is the main aim of physiotherapy and return to activity. This is done through controlled stretching, strengthening exercises and where appropriate, manual therapy (Walkzak, Johnson & Howe, 2015).
Your body will reabsorb the calcified tissue, however in rare cases where this is not occurring, referral to an orthopaedic surgeon may be necessary. Whilst there is generally a good prognosis for MO, there are some cases where it can take up to a year to resolve.
In some cases, Shockwave Therapy in conjunction with rehabilitation exercises has been shown to allow a faster return to sport (Buselli et al., 2009). Make sure you check with us to see if you’re an appropriate candidate for shockwave as we offer this service at our Kew and Footscray clinics.
References:
Torrance, D. A. (2011). Treatment of post-traumatic myositis ossificans of the anterior thigh with extracorporeal shock wave therapy. The Journal of the Canadian Chiropractic Association, 55(4), 240.
Buselli, P., Coco, V., Notarnicola, A., Messina, S., Saggini, R., Tafuri, S., … & Moretti, B. (2010). Shock waves in the treatment of post-traumatic myositis ossificans. Ultrasound in Medicine & Biology, 36(3), 397-409.
Walczak, B. E., Johnson, C. N., & Howe, B. M. (2015). Myositis ossificans. JAAOS-Journal of the American Academy of Orthopaedic Surgeons, 23(10), 612-622.
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