A Diagnostic Mystery

Ok, my medical world friends, help me out. I got a phone call from a friend last night and I'm puzzled.

We'll start with:
27 y.o male presenting with complaints of spontaneous "shooting" left sided knee pain for two weeks. He denies traumatic event.
Pain started as "an ache" in his knee which he ignored. Ache worsened over three days until he was walking on the third day and could no longer straighten his leg completely, causing him to limp.
Joint mobility worsened to the point of inability to bear weight.

At this point he went to the doctor. Doctor guessed torn meniscus and ordered an MRI.

The MRI came back with no damage to the meniscus. The nurse in radiology said "looks like pre-patellar bursitis," but that too was ruled out by the doctor.

Then the patient went home and developed the following new symptoms:
- swelling in foot (left side)
- foot cold to touch
- positive pedal pulses

The doctor ordered "blood work," and told him to go home and if the results came back for a positive clot, to go to the ER. The results were negative.

The newest idea is that it might be a degmoid. So the doc gave him an oncology referral which he is now waiting on.
The meds he came home with are:
Vicodin 5/500mg 2 tabs q 8 prn and
Neurontin 300mg p.o t.i.d
He's been shunning both and taking Advil.

My questions are:
- I'm assuming the "blood work," was a D-dimer test, but my friend doesn't know. That's not a test that's 100% accurate to my understanding... and additionally they didn't do a CT scan or a venography. So, can they really rule out a DVT? He's a young, non smoking healthy young man with a very active (rock climbing , scuba diving) lifestyle, however he just got back from a plane trip to Europe.

- Why wouldn't a degmoid have showed up in the MRI? Especially if it's big enough to be (apparently) crushing a nerve and compromising circulation?

- What is the prevalence of degmoids in joints? I've only really read about them in relation to the ovaries or to cartilage (like the nose or ear). And what would the next step be if it is a growth?

- Do you have any other ideas?

Thanks for any help you can dig up, guys.
Dr. House wouldn't pick up his phone when he saw it was me calling.