Your note says S43. as an ankle sprain, but S43 is for the shoulder region, so I am assuming that is a "typo."
Assuming that there is no new or recent injury to cause the more recent/current increased ankle pain and swelling, then I would relate it back to the original injury, "lateral ankle sprain" and use S93.49 _ S (6th Character 1 for right, 2 for left, your note doesn't say which), and S for Sequela from the original injury. I recommend 5th Character 9 for "Other ligament/s" of the ankle. The most commonly "sprained" ligament of the ankle is the Talo-fibular ligament, which for some bizarre reason in ICD-10 is not listed a "specified" ligament in the Ankle Sprain Code Set, so it has to be allocated to "Other" (i.e. "none of the above").
As for the "swelling" of the ankle, the Alphabetical Index of Diseases refers "Joint Swelling" to Effusion of the joint. Also, "Edema" of the ankle refers to Effusion of the joint. Unfortunately, most residual ankle swelling from previous injury is in the extra-articular soft tissues (edema) and not intra-articular (effusion). Unfortunately, I am not able to resolve this particular dilemma of semantics, so you would have to go with M25.47 _ (6th Character 1 for right, 2 for left).
The ankle "pain" has only one possibility, M25.57 _ (again 6th Character 1 for right, 2 for left), for Ankle Joint Pain, and which doesn't really differentiate acute from chronic pain, which this would be at this time. This could be supplemented with G89.21, Chronic pain from previous trauma, since the patient is being seen for bot "ankle pain" and "swelling."
The Sequencing would be the pain and swelling codes first, and ending/finishing with the Ankle Sprain code with S.
I will be interested to see what others might have to say.
I hope this is helpful.
Respectfully submitted, Alan Pechacek, M.D.
icd10orthocoder.com