After sustaining a career-threatening injury in February, David Clarkson has set off on the long road to rehabilitation. He has invited the Sunday Herald to follow him on his journey over the next few months. It is going well, so far. He’s already learned how to walk again.

DAVID Clarkson's Motherwell jersey from the 2007/2008 season hangs on the wall at the far end of his hallway. It is the shirt that has Phil O'Donnell's autograph embroidered into the chest. Its presence there has a simultaneous purpose. It is a memorial to his uncle who died in front of him on the Fir Park pitch during a match against Dundee United at Christmas 2007. It is also a constant reminder of life's priorities.

On this bright May day, the Clarkson household is a metaphor for Clarkson the player. It is busy and energetic. Wife Natalie flits from room to room, refilling cups of tea and organising the day ahead. She has just returned from taking their six-year-old son Joshua to school. There are brief discussions with David; his three-year-old daughter Jessica floats around the living room at the front of house, returning every once in a while to her dad's side. The Clarksons are having a new bathroom fitted upstairs. The distant sound of a drill punctuates the conversation. It is a fitting reminder that rebuilding has been a common theme in this household over recent months.

Clarkson has been confined to a lounger in the front room of his well-appointed sandstone Hamilton home for almost 12 weeks. He has been recuperating from the effects of an accidental collision with Billy O'Brien, the St Mirren goalkeeper, during a training session at the end of February. It left Clarkson lying crumpled on the grass, not fully aware of the significance of what had just happened. Specialists call the trauma experienced by Clarkson "a hyperextension of the knee combined with a rotational varus force". In simple terms, his right knee did things knees are not designed to do.

Clarkson is pondering the question: is he afraid of the future? He’s been asking himself that a lot since his world and - almost literally - his knee was turned upside down in that training-ground collision in February. He keeps returning to the same answer.

“I wouldn’t say I’m afraid,” he says. “I do think about whether I am going to play again. I do think ‘is everything going to be all right, is it going to go to plan? In nine months or a year's time, when I am due to come back, is everything going to be all right?' I don't know if that's a fear or just a thought process. It's maybe too early for that because there is so long to go and I have just started doing the rehab. It's very limited stuff that I'm doing just now. Maybe when I am halfway through that's maybe the stage when the fear kicks in and I say 'is this going to be the same as it used to be? Will I be able to play to the levels that I have done for my full career?'

“It was a nice day, the sun was out, it was a bit cold but everything was normal,” he recalls of the fateful day. “I can remember driving to Paisley and I was thinking ‘thank goodness the sun’s out’. I was looking forward to training. It was a typical training session really. It was coming to the end; a ball was crossed in over my shoulder and I went to volley it. I heard the shout ‘keeper’s’ and as I went to hit it my leg was going one way and Billy was coming the other way and I hit the deck.

“It seemed like I was lying on the ground for a lifetime but it was probably only a minute. I don’t really stay down. I thought it was just a bad knock. Normally, I’m straight back up and I just get on with it. The physio [Gav Lee] came over to help me but as I stood up and went to put pressure on my knee, my leg gave way.”

There was a wait at the training ground until he was transferred to hospital. With Clarkson nearing the end of his St Mirren contract and no guarantee of a new one with the club fighting for Championship survival, there was a difficult, distressed phone call to Natalie, too.

“There were so many questions and I didn't have any answers. There was a lot going through my mind at that time: 'is it broken? My deal's up in the summer. I hope this isn't bad. The position St Mirren are in as well I don't want to miss out on being part of helping the boys [to stay up]'."

Clarkson’s diagnosis was as blunt as the blow that had taken him to Ross Hall Hospital in the first instance. He had suffered significant damage to the posterolateral corner (PLC) in his right knee, a trauma injury usually found in contact sports and car accident victims. Though rare, it can have a devastating effect on athletic performance. The bad news did not end there for Clarkson. PLCs rarely occur in isolation. Clarkson, aged 31, had also torn his anterior cruciate ligament.

The sound of the drill whirrs again as Clarkson talks about his operation. He had both the ACL and PLC completely rebuilt by surgeon Colin Walker, an expert in ligament reconstruction, at Glasgow's Queen Elizabeth Hospital. Tendons from his hamstring were inserted in his knee to replace the mangled ligaments.

Perhaps the most shocking aspect of Clarkson's injury is the heavy toll it has extracted on a hitherto healthy body. This is the unseen side of injuries to sportsmen and women. We view them as physically superior but in the final analysis they are flesh and bones like the rest of us. Clarkson confesses he was taken aback by the extent of what his rehabilitation would entail. He is now on his second leg brace, a contraption which looks as if it could be a medieval torture device, but he is off his crutches.

“I've literally had to learn to walk again. That was the first part of my rehab. You lose all the strength in your knee and thighs. There was a tremendous amount of effort to get to that point. When you've been walking your entire life you don't think it will be any different but it was naïve of me. It was literally baby steps. I took a video of it just to try to see how far I've come. It might just be little bits but that's what I've been encouraged to do as one of the stages of my rehab.”

Clarkson is posing for pictures, now. He’s laughing, asking whether he should keep the legs of his shorts hoisted up or dropped down. He shows me pics on his mobile phone of his knee post-op. It is the size of a small grapefruit. The knee is still swollen but it requires close inspection to see a discernible difference with his left. A seven-inch scar, still pink and shiny from the surgery traces its way down the outside of Clarkson's knee.

“I can do one of both and then you can decide,” he laughs again. This is not the comportment of a man who is battling back from serious, career-deciding injury but then Clarkson has never been one for navel gazing. After what happened to his uncle Phil, he is determined to remain positive.

“I think that comes from the fact that we have a massive family. We're all easy come, easy go. I'm glad I'm like that, to be honest. I was never one for getting up tight or putting myself through the mill when times were hard. I just tried to get through them. I don't know whether it's a good thing or a bad thing. It surprises some people as well because it is such a bad injury. But I like a laugh and a joke. It doesn't mean I'm not frustrated. I haven't felt depressed. Maybe I haven't got to that stage yet and hopefully I won't get to that stage. That's when you start thinking 'what if?'"

Clarkson admits he enjoys relaxing but even he has struggled with the interminable boredom of 14-hour days in front of the television watching box-sets. Nevertheless, he has diligently observed his recovery plan. Natalie follows him every time he walks upstairs. The fragility of a footballer's career is perhaps no more apparent in this mental image. But Clarkson is a father, too. He is required to be on his feet and fully operational for more than just financial reasons. There are daily chores to be carried out, parental responsibilities – and he has been unable to fulfil his.

“It's every day stuff, bathing the kids, putting them to bed, giving them their breakfast, taking the wee man to school or his football, taking Jessica to her dancing. It’s left to the rest of our family. I get Joshua asking me when I'm going to take him to his football or when I'm going to take him to school. 'Can you pick me up from school?' 'When's your leg going to be better?' They're asking the kind of questions young kids ask. It's been affecting them as well. They think it's going to be better tomorrow.”