In this study, we wanted to investigate whether the severity of preoperative degenerative changes in the trapeziometacarpal (TM) joint seen on CT scans would influence the clinical outcomes after total TM joint arthroplasty, and particularly whether discrete degenerative changes in the scaphotrapezial (ST) joint would negatively affect the clinical outcome. Patients classified as Eaton–Glickel stage 2 or 3, as well as patients with Eaton–Glickel stage 4 disease who had discrete degenerative changes in the ST joint (i.e., narrowing and sclerotic changes but no osteophytes) were included in the study; patients with more severe degenerative changes of the ST joint were excluded. Follow-up was done using the Disability of Arm, Shoulder and Hand (DASH) score at 3, 6 and 12 months after surgery together with grip strength and pain using a 100-mm visual analog scale. In all, 59 patients with 69 total joint arthroplasties were included in the study; there were 47 females and 12 males with a mean age of 59 years (range 41–77). We found no significant difference between the three patient groups in their improvement in grip strength from preoperative to 12 months. Also we found no statistically significant differences in the DASH score or pain level at rest or during activity between the preoperative and all the postoperative time points. Total TM joint arthroplasty can produce excellent short-term clinical results with a good restoration of grip strength and function. Discrete degenerative changes in the ST joint appear not to be a contraindication for treating TM joint osteoarthritis with total joint arthroplasty.