Dr Manish was diagnosed with COVID-19 in September, and went on to suffer from interstitial pneumonia.

Although his symptoms were severe, they lasted a standard 15 days after which he recovered completely.

"After one and a half months, I started having pain in my left hip joint," he says.

After months of persistent pain, Dr Manish was diagnosed with AVN (avascular necrosis), of the hip, stage 2 after months of escalating pain.

Dr Manish, however is not the only one. An increasing number of COVID recovered patients across the country are reporting the rare post-covid complication. There is, however, no official data for this yet.

What is AVN? How is it linked to COVID-19?

FIT speaks to Dr Sanjay Agarwala, Head of Orthopaedics at the P.D. Hinduja National Hospital, Mumbai, who has done extensive research on the subject.

First a quick run down of what AVN (avascular necrosis) is.

Simply put, AVN is the death of bone tissue, that affects the bones of the hip in particular.

AVN, he adds, usually occurs in those between the age group of 15 to 45 and is rare in children. "The only time I've seen AVN in children is when they are suffering from leukemia."

What generally causes AVN?

AVN, Dr Agarwala explains, usually happens because of kinks in the blood vessels in the area. "That part (hip) is more prone to such kinks because of the hairpin bends in the area. These kinks or clotting can lead to bones in that sector dying," he explains.

"The hip bone is also in a weight baring area," he adds. "And when that starts collapsing is when you start getting problems."

Whether COVID can directly cause AVN is yet undetermined. But it could be a potential cause, says Dr Agarwala. "In the past year or so we have seen how COVID can impact blood vessel."

On the other hand, "that use of steroids can cause AVN has been established for years," he adds.

The link with Steroid based treatments

Much has been said about steroids and how it can lead to other post COVID complications, including a number of fungal infections that come in every colour of the rainbow–the most notable being black fungus.

"It is lifesaving. I'm not saying you musn't use steroids. But If you have had COVID and have been on steroids, you have a higher propensity to get AVN," Dr Agarwala clarifies.

A study led by Dr Agarwala further points to COVID patients who took smaller doses of steroids also coming back with AVN, and that it generally takes 6 months to year post steroid exposure for AVN to develop.

Depending on the stage of the condition, AVN may require medical support or hip replacement.

Dr Manish was advised by orthopedic surgeons to get surgery done before he connected with Dr Agarwala. "He was confident that stage two, AVN is curable with conservative management, without surgery."

"Dr Agarwala put me on an IV medication and some oral medicines and now after 6 months, my pain has decreased by around 40 percent," adds Dr Manish.

It can be hard to catch it in the early stages, though, as there are not many early signs or symptoms of AVN, except groin pain and discomfort in the hips.

Moreover, X-rays aren't able to pick up on AVN in the early stages.

This is when Dr Manish's Doctor's instincts kicked in. "I realised this was not just a routine pain. I went back and got an MRI done."

There are 4 stages to the disease.Dr Agarwala explains these as being,

• Stage 1 - cannot be detected on X-ray, but can be diagnosed with an MRI scan.

• Stage 2 - Can be just about made out on an X-ray, but MRI confirms it. At this stage, according to Dr Agarwala, it is possible to reverse the condition with medication.

• Stage 3 - The bone as collapsed and it can be seen on an X-ray.

• Stage 4 - You would need a hip replacement.

"As a doctor I was aware of the rare possibility of COVID causing AVN, but for a normal person, they may not correlate a hip pain or a bone pain to COVID," he added. "They may go unnoticed."

"We think COVID is an illness of the lungs. No body thinks that it could affect our bones and joins also," he adds.