Vita TU, Ocupational Therapist and Project Manager,
Sunshine Social Welfare Foundation
In burn rehabilitation, our constant concern is the impact that burn scars have on joint mobility and by extension, on the functional independence of our patients. When dealing with hand burns, we may prioritize MP joints. When dealing with lower limb burns, we may prioritize knee joints. However, when the range of motion of a single joint improves, does it also mean that overall functional performance improves as well? Only focusing on single joints risks making us overlook the big picture, so it’s also important to look at multiple joints together.
Functional movements involve multiple joints
The first reason is that the execution of functional movements in the human body is almost always a combination of coordinated movements of multiple joints that move at the same time. Let’s say you reach for an object that is farther from you. The smooth movement of extending your arm, reaching and grabbing the object is the result of your shoulder and elbow joints coordinating to extend the arm, while your wrist and finger joints coordinate to grab the object. Therefore, in addition to focusing on the movement of a single joint, we must also pay attention to the smoothness of simultaneous movements by multiple joints.
Functional movements recruit skin close to and further away from the joint
The second reason of particular concern for burn patients is the effect of scars on multiple joints.It is well known that contracture affects joint mobility at the site of the scar. But even if scars are not located directly on joints, they can still affect range of motion on adjacent joints. This is because during joint movement, it doesn’t just recruit the skin around it. Look at the picture below. Which part of the skin do you think is recruited when performing neck extension?
Read on to know the answer...
Because the skin is a continuous unit, even the skin further away from the joint will also be recruited. A study by Richard et al. in 2009  found that during shoulder abduction, even the skin of the abdomen was recruited by the movement. In the example above, neck extension recruits skin over the neck, the chest and all the way to the abdomen.
Skin close to the joint and further away from the joint is recruited, so the more joints move at the same time, the wider the adjacent skin area is recruited to make the movement. However, scars contract towards the center, pulling the skin around it. Also, scars do not have the same elasticity as normal skin and cannot be stretched easily. When multiple joints in close proximity move at the same time in the opposite direction of scar contracture, the demand on scar pliability will be higher than for a single joint movement. Because the scar cannot stretch, movements will be restricted.
Because of the above-mentioned reasons, performance of movements post-burns cannot only focus on single joints, otherwise we risk overlooking problems. When one joint achieves full range of motion, it does not mean it can achieve ideal range of motion when involved in a multiple joint movement. For example, a patient with upper extremity burns can achieve full range when performing forearm supination during elbow flexion. However, performing forearm supination when his shoulder is placed in 90 degrees flexion and elbow in extension will feel very tight. It will be even more difficult if we also ask the patient to perform thumb abduction at the same time. In a case like this, if we only look at individual joint movements, we would think that the rehabilitation goals have been achieved. In reality, when the patient returns to his normal life, scars will create limitations when he tries to extend his arm to grab things (ex: reaching to grab an object on a shelf over his head) or when he manipulates objects with his hands at a distance from the center of the body (ex: holding the handles while riding a bicycle).
Therefore, when assessing or designing rehabilitation activities, the therapist should consider the movement performance of activities involving multiple joints and how scars can impact these joints. This is especially important in the middle and late stages of rehabilitation. If necessary, rehabilitation can be combined with surgery to release the scars, so as to achieve the best functional performance after burns.
By the way, the answer is C!
1. Richard et al. Identification of Cutaneous Functional Units Related to Burn Scar Contracture Development. J Burn Care Res 2009;30:625-631