Uusi pohjallinen auttaa, koska kantapääni tulee kipeäksi pitkällä kävelyllä.

Pohjallinen means insole.

In uusi pohjallinen auttaa, it is in the nominative singular because it is the subject of the sentence: the new insole helps.

• uusi = new
• pohjallinen = insole

The adjective uusi matches the noun in number and case.

This is the most neutral Finnish word order: subject + verb.

• uusi pohjallinen = the subject
• auttaa = the verb

So the structure is simply:

• Uusi pohjallinen auttaa.
• A new insole helps.

Finnish word order is flexible, but this is the basic, unmarked way to say it.

Auttaa means to help.

Here it is used without an expressed object, in the sense of is helpful / helps:

• Uusi pohjallinen auttaa.
• Literally: A new insole helps.

Finnish often allows this kind of use without saying exactly what it helps with.

It can also take an object in other sentences, for example:

• Se auttaa minua. = It helps me.

Koska means because.

It introduces the reason:

• Uusi pohjallinen auttaa, koska...
• A new insole helps, because...

So the second clause explains why the insole helps.

Because koska starts a subordinate clause.

Finnish normally separates this kind of clause with a comma:

• Uusi pohjallinen auttaa, koska kantapääni tulee kipeäksi...

This is very similar to English punctuation with because, although Finnish comma rules are in some ways even more regular.

Kantapääni means my heel.

It is built like this:

• kantapää = heel
• -ni = my

So Finnish often expresses possession with a possessive suffix attached directly to the noun.

Examples:

• käteni = my hand
• jalkani = my leg
• kantapääni = my heel

This is one of the most common things English speakers notice in Finnish.

Yes.

• kantapääni = my heel
• minun kantapääni = my heel

Both are possible. The version with just -ni is often enough by itself. Adding minun can make it more explicit, more emphatic, or just more natural in some contexts.

So in this sentence, kantapääni is completely normal and natural.

Literally, it means my heel becomes sore.

This is a very common Finnish pattern:

• tulla + adjective in translative (-ksi) = to become ...

So:

• tulee kipeäksi = becomes sore / gets sore

This is why the sentence does not use a direct equivalent of hurts here. Finnish often expresses the idea as becomes sore/painful.

Because -ksi marks a change of state.

• kipeä = sore
• kipeäksi = into a sore state / sore

After tulla when you mean become, Finnish often uses the translative case:

• tulla iloiseksi = become happy
• tulla valmiiksi = become ready / be finished
• tulla kipeäksi = become sore

So kipeäksi is the correct form here because the heel is becoming sore.

It is in the translative case.

The translative usually ends in -ksi and often expresses:

• becoming something
• changing into a state
• the result of a change

Here:

• kipeä → kipeäksi

That tells you the heel is not just sore in general, but that it gets sore.

Pitkällä kävelyllä means something like:

• on a long walk
• during a long walk
• while walking for a long time

It is a very natural Finnish way to express the situation in which something happens.

So the meaning is not that the heel hurts because of the concept of walking, but specifically during a long walk.

Because the adjective has to agree with the noun.

• pitkä = long
• kävely = walk, walking

In this phrase, both are in the adessive case:

• pitkällä
• kävelyllä

This is normal Finnish adjective agreement: the adjective usually matches the noun in case and number.

Kävelyllä is in the adessive case.

The adessive often has endings like -lla / -llä and can mean things like:

• on
• at
• during
• in the course of

Here it gives a context like on/during a long walk.

So pitkällä kävelyllä is not literally about being physically on top of a walk. It is just the Finnish idiomatic way to express the circumstance.

Here kävely is a noun.

It comes from the verb kävellä = to walk, but kävely means:

• walking
• a walk

So in this sentence:

• pitkällä kävelyllä = during a long walk

This kind of action noun is very common in Finnish.

Yes. Finnish has several ways to express this idea.

For example, you might also see something like:

• pitkän kävelyn aikana = during a long walk
• kun kävelen pitkään = when I walk for a long time

But pitkällä kävelyllä is very natural and compact.

In Finnish, tulla kipeäksi is a very normal way to express getting sore.

English often prefers verbs like:

• hurts
• starts to hurt
• gets sore

Finnish often uses a change-of-state structure instead:

• kantapääni tulee kipeäksi

So even if it may feel a bit indirect to an English speaker, it is completely natural Finnish.

It has two clauses:

1. Uusi pohjallinen auttaa

   • subject: uusi pohjallinen
   • verb: auttaa

2. koska kantapääni tulee kipeäksi pitkällä kävelyllä

   • koska introduces the reason
   • subject: kantapääni
   • verb: tulee
   • complement: kipeäksi
   • adverbial phrase: pitkällä kävelyllä

So the sentence is basically:

• [Main clause], because [reason clause].

That is a very common and useful Finnish sentence pattern.