Ian or Craig why does this matter ? Ie what is a cross sectional or prospective design when it gets up in the morning and how does it change this re the above paper ?
Off topic but would like to know and too lazy to add to my reading list at the min.
Prospective:You measure dorsiflexion stiffness at ankle, then follow cohort for period of time and see who develops PF. Run stats.
Cross-sectional: Your cohort already has PF, and you measure dorsiflexion stiffness at ankle. Run stats.
Prospective design will be much more valid at suggesting causation.
You can't infer causation from a cross-sectional design, you can only conclude there may be a correlation.
So in this case we cannot conclude from this study that tight gastrocnemii are a risk factor for PF. (As it may be that PF causes tight gastrocnemii for example)
With a prospective study design, you can deteremine causation and risk factors
With a cross sectional study design, you can only get correlations.
The above study was cross sectional and they only showed a correlation between plantar fasciitis and tight gastrocs. From this cross sectional design you can not determine if the tight gastrocs caused the plantar fasciitis or the plantar fasciitis caused the tight gastrocs. A prospective study design would deteremine what caused what.
The authors above claimed it was a prosepctive design when is was only cross-sectional. However, they were appropriatly cautious in stating the conclusion:
and also, the gastrocs are tight, so if its a "chicken or egg" probably does not matter clinically, as they need stretching and/or heel raise, and/or the fibula mobilized, and/or a surgical lengthening (Gastroc recession cured 93.6% of chronic plantar fasciitis)
I would imagine that most prospective studies require a large cohort if the idea is to see if the risk factor is causal (?) in the pathology. That would lend it greater validity also?
Correlation Between Gastrocnemius Tightness and Heel Pain Severity in Plantar Fasciitis
Christopher J. Pearce, MB ChB, MFSEM (UK), FRCS (Tr&Orth), Dexter Seow, MB BCh, Bernard P. Lau, MB BCh BAO, MRCS Foot & Ankle International September 13, 2020
Clinical measures of foot posture and ankle joint dorsiflexion do not differ in adults with and without plantar heel pain
Karl B. Landorf, Michelle R. Kaminski, Shannon E. Munteanu, Gerard V. Zammit & Hylton B. Menz Scientific Reports volume 11, Article number: 6451 (2021)