Pros
High Quality
Good Ingredients
Established Brand
Cons
The exact dose of each ingredient used is not listed
Expensive
There's obviously a lot of ingredients in Penetrex joint & muscle therapy cream that are only there to make it an actual cream, so we'll leave those out of the ingredients section. Oil and water for example aren't particularly relevant to how well it works for joint and muscle relief.
Arnica - Arnica is the star of the show and is the most well backed for topical use [1] it's been run in multiple double blind trials comparing it to over the counter pain killers where it performed comparably. Now, this isn't going to do much for any severe joint pain, but can help with muscular issues without any doubt.
MSM - This ones a little up in the air, it dose work, but most of the backing is in relation to inflammation via sunlight specifically. Now, this is great it you're somewhere warm, or the pain is in an exposed area. It typically is used for joint pain relief, but orally not topically, where MSM is more well backed.
Glucosamine - It has been shown to be more effective than placebo at relieving pain against a placebo [3]. Glucosamine is normally taken orally for joint pain, although it does seem to have some effectiveness as a joint pain reliever. Similar results came as a muscle therapy cream, but it's less well backed.
Boswellia - Boswellia is pretty potent when taken orally as an anti-inflammatory [4] there is some backing for it's use in a recovery cream and it is actually very good for your skin, but there's not enough evidence to suggest it's great. The little we do have seems to be initially positive though.
Vitamin b6 - There's not a lot of evidence to back vitamin b6's use as a topical for joint pain, however, there is reasonable evidence to suggest it is successfully absorbed through the skin [5]. And there is some evidence that b6 can reduce inflammation when consumed orally. So yes it should have an effect, it just probably doesn't matter where it's rubbed and won't work much better by being applied to the site. That's not a bad thing, just worth mentioning that getting from a supplement would be fine too.
Aloe Vera - It's aloe vera, it's reasonably well backed, and it's reasonably common knowledge that it has a soothing effect on muscle soreness so it's a solid inclusion in penetrex joint & muscle therapy cream.
1 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5372953/
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8537440/
3 - https://ebm.bmj.com/content/8/5/154
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3309643/