Lame/Limping Chook - advice please

[bekabat]

Looking for any advice to try and work out what's happening with our chook. It's a young Light Sussex (potentially a roo but not entirely sure yet) who is 6 months old. About 5 days ago, it started hobbling and it's left leg seemed weak. It would bumble around the pen and rest a lot down on the elbow of the leg. It is otherwise quite alert, is eating and drinking and still wants to get out and free range at the end of the day. It has taken to sleeping on the nesting shelf so obviously roosting is difficult. There doesn't appear to be any swelling of the foot but there was a very small hard lump near one of the toes. Manipulation doesn't appear to cause any pain. When it walks, the toes seem stiff and the leg is straight (does a bit of a German goose step type movement with it) but then the foot goes a bit weak and slack and it looses the strength to stand on it. There's no progression or improvement.
Having looked through a multitude of posts I am confident it isn't Marek's but I am getting confused with all the other potential issues people have mentioned ie: mites, worms, coccidiosis etc etc....
Thanks in advance for any thoughts...

 

[Eggcessive]

I think it possibly could be Mareks, but there can be a lot of conditions that can cause lameness, such as injury, bacterial or viral arthritis, bumblefoot, mycoplasma synovitis (MS,) and others. Could you show a picture of the hard lump near the toes.

 

[bekabat]

I'll attempt to get a photo later today - I feel like I'm stressing it out if I try to catch it. I also noticed this morning that there seems to be less of an attempt to keep the leg out and straight when walking. The foot is now floppy and turned under like a paralysis so I guess it's getting worse