Only rheumatologist or orthopedic answer. Some hypermobile joints from activites, some born with? Can these loose joints make normal joints loose?

No. "loose joints" are typically genetic, rarely post trauma and never a result of other joints being loose. Most commonly shoulders knees and fingers are affected.
No. Laxity or 'loose - jointedness' is generally inherited in a multifactorial fashion.Trauma can 'cause ' loose joints ( shoulder, knee mostly); but 'mild' injury will not cause 'loose joints' in non- lax individuals(if that makes sense). Almost all loose- jointed people are born that way; instability occurs w/ sports and mild injury(shoulder esp.)in 'loose- jointed people' thumb>forearm distance min.

Related Questions

Just orthopedic or rheumatologist answer some hypermobile joints from ballet, gymnastics. Can these loose joints make the normal joints loose?

Not really. Genetic predisposition , activities and injuries can lead to hypermobility of a joint . A a loose joint above or below a normal joint will protect it from being over stressed at time and if any thing would prevent it from becoming hyper mobile. Read more...
Loose joints. Indirectly, you are putting additional stresses on muscles, tendons, ligaments, and joints above a loose joint. If well-trained, you can accommodate for these weaknesses. Read more...