This person had a congenital “club foot” at birth also know as congenital talipes equinovarus (CTEV). It is a congenital deformity involving one or both feet. In this case it affected the right foot (the smaller one).
Foot size is often measured with the Brannock device in shoe stores, you know, the weird looking thing with the slider that measures foot length and width. In this case, the right heel:ball ratio, the length from the heel to the first metatarsal head, is shorter. The heel:toe length is also shorter, nothing like stating the obvious ! IF they are shorter then the plantar fascia is shorter, the bones are shorter, the muscles are smaller etc.
So, the maximal height of the arch on the right when the foot is fully supinated is less than that of the left side when also fully supinated (ie. during the second half of the stance phase of gait). Even with maximal strength of the toe extensors which we spoke of yesterday will not sufficiently raise the arch on the right to the degree of the left.
Thus, this client is very likely to have a structural short leg. Certainly you must confirm it but you will likely see it in their gait if you look close enough.
Also, you must remember that the shorter foot will also spend fractionally less time on the ground and will reach toe off quicker than the left. This may also play into a subtle limp.
This client may have a mal-fitting shoe, the right foot will swim a little in a shoe that fits correctly on the left. You may be easily able to remedy all issues with a cork full length sole insert lifting both the heel and forefoot. This can negate the shoe size differential, change the toe off timing and remedy much of the short leg issue. You will know that the right foot at the metatarsal-phalangeal joint bending line will not be flexing where the shoe flexes on that right foot. The Right foot will be trying to bend proximal to the siping line where the shoe is supposed to naturally bend. This will place more stress into that foot. This brings up the rule for shoe fit: never size a persons shoe by pinching the toebox to see if there is ample room, the shoe should be fit to meet the great toe bend point to the flex point of the shoe.
Strength of muscles is directly proportional to the cross sectional area of the muscle. With smaller muscles, this right limb is very likely to be underpowered when compared to the left.
All of these issues can cause a failure of symmetrical hip rotation and pelvic distortion patterning.
Altered arm swing (most likely on the contralateral side) is very likely to accommodate to the smaller weaker right lower limb. Do not be surprised to hear about low back pain or tightness or neck/shoulder issues.
A shorter right leg, due to the issues we have discussed above, will place more impact load into the right hip ( from stepping down into the shorter leg) and more compressive load into the left hip (due to more demand on the left gluteus medius to attempt to lift the shorter leg during the right leg swing phase). This will also challenge the pelvic symmetry and can cause some minor frontal plane lumbar spine architecture changes (structural or functional scoliosis…… if you want to drop such a heavy term on it).
Gait plays deeply into everything. Never underestimate any asymmetry in the body. Some part as to take up the slack or take the hit.