If he has feelings of the joint being loose - it could be a ligament or tendon that has weakened. Ligaments and tendons are elastic so they can feel a bit like a "rubber band"
Rt&Lt thumb arthroplasty 2012 ; RT TKR & Bilat CTS 2011
Fusions: L5-S1 (87), L4-S1 (93), C5-C7 ('06), L3-S1 ('10)
C5-C7 foraminotomy 08