This is a pictograph of an adult person with the addition of the verb to point. In an equine, lameness may be indicated by a change in stance known as pointing. It will also manifest in a change of gait. Hence, it is easy to understand why this Indus sign is an ideograph for the adjective lame.
Mahadevan's sign number 41 is related to the Chinese character wāng 尢.
Illustrative Text References:
Harappa: Seal: H-1673 A (NB. image H-1673 A is a view of the seal as opposed to the sealing, and is therefore a mirror image of the inscription): Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 235: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Lohumjo-daro: Seal: Lh-1 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 357: Collections in India: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 41: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.