In honour of the special occasion, the actress opted to upload a glamorous selfie to her Instagram Stories alongside the caption: "Last week marked my 43rd year around the sun and I'm much happier about it than I look in this photo."
She went on to say: "Thanks for all your birthday love! [white heart emoji]. No filter, just @dr_marwaali and #photofractional laser treatment."
In her selfie, Joanne was pictured looking particularly glamorous with her blonde locks styled in loose waves around her shoulders.
Embracing her natural beauty, the TV star highlighted her features with a radiant beauty blend comprising subtle bronzer, defined brows, fluttery lashes and a dab of glossy nude-pink lipstick.
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Joanne accessorised with layered gold necklaces and opted to wear a cosy yet stylish black jumper for the perfect autumnal outfit.
Whilst the actress has been noticeably quiet on social media, Joanne is thought to be on cloud nine with her rumoured beau, Mark.
In images obtained by MailOnline, the Downton Abbey actress was seen strolling hand-in-hand with her new partner earlier this month whilst walking in the Buckinghamshire countryside.
Dressed down in black sportswear and a raincoat, Joanne appeared to be in relaxed spirits as she walked alongside her beau and their pet pooch. Although not much is known about the star's new romance, it seems this is her first relationship since her split from her ex-husband, James Cannon.
The former couple confirmed their split back in February 2020, just before the world went into lockdown amid the global COVID-19 pandemic.
In spite of her marriage breakdown, the 43-year-old previously revealed that she is "grateful" for what she has.
Speaking to Red Magazine, she candidly said: "I didn't think I'd be divorced, I didn't think we'd be going through a pandemic, I didn't think my life would be in flux in the way it was. But I'm OK with that."
Since their split, Joanne has taken over the former couple's joint production company called Run After It.
"I've taken that over now, so I'm running my own company," she explained.
"I'm excited to move forward with it and get my head around the direction in which I want to take things. We've already had a script commissioned by Sky. It feels like an exciting new chapter."
Reflecting on the importance of friends and family, Joanne went on to say: "I'm so grateful for my friends and family, for my health and to have been working so much during this past year. You realise, when it comes down to it, how many positives you have in your life."