The scar on her right knee is small, but when Rachel Yang awakes each morning, she feels its weighty significance in her 35-year-old bones.

Injury is the athlete's unwanted yet inevitable companion. For most, competing while at 100 per cent fit is a rarity.

Yet it has been 13 months since Yang tore her anterior cruciate ligament (ACL) in a freak accident during pole vault training. With no cross bar available, she had used a TheraBand instead. But she got her legs entangled in it and twisted her right knee awkwardly in the process of trying to free herself.

"After I heard the pop, my heart sank and my world came crashing down," she recalled with a sigh.

"The moment I came down and hobbled to the track, I started calculating and asked myself, 'Do I have enough time to qualify for the SEA Games?'"

Single-mindedness is the very essence of Yang, who was dismissed for being too old (the former schools badminton and volleyball player picked up pole vault late, at the age of 20) and too small (she is 1.57m) early in her career.

She ignored both criticisms to become Singapore's top female pole vaulter. She owns the national record (3.91m) and is the country's first female SEA Games medallist in the sport, after her silver at the 2015 edition in Singapore.

A tenacious attitude was required after this latest knee surgery - she tore the ACL in her other knee, the left, in 2002 during her first pole vault training session - but Yang was fully committed physically.

She said: "The qualifying mark was 3.60m, and I knew with proper rest and training I should be able to make it. I didn't stop training. In fact I trained even more as I had rehab sessions as well."

The mental barriers were tougher to overcome. Yang recalled: "I was scared. I dared not sprint or jump for fear of tearing the graft. Six months after the surgery, I couldn't do a proper single leg hop and the physios were worried."

In some ways, she still retains the scars, both literally and metaphorically, created by these setbacks.

"The experience of the first ACL injury helped because I knew what it took to come back from it," she explained. "But this recovery felt longer, maybe because of my age, and I became anxious as I would compare my progress and feel like I was behind schedule."

In February's Singapore Athletics Track and Field Series 2, her first competition since the injury, Yang failed to clear 3.2m and felt depressed, struggling to find motivation.

Encouragement from her physiotherapists and her husband/coach David Yeo was critical during this period. Yeo said they worked a lot on visualising techniques and focused on improving her form in mid-air as she propelled her body over the bar.

He added: "She can't generate as much speed as before but her technique is better now and that helps her to clear greater heights."

Learning to adjust after a serious injury is a necessary facet of an athlete's life. In Yang's case, that meant altering her run-up.

Before the injury, she stood 25m from the vault box, took 14 strides and used a 4.3m pole. Now with less explosiveness in her legs, she stands closer, 18m away, and takes 10 steps with a 4m pole.

In training now, she completes about five full jumps whereas she used to do between 15 and 30.

Her ambition of winning gold has not changed though. Not only did she clear 3.91m and set a new national record at the Thailand Open in June, but she also won the competition and beat rival Chayanisa Chomchuendee, the 28-year-old Thai who won golds at the 2013 and 2015 Games.

Yang said: "I hope to break the 4m barrier in Kuala Lumpur. If I do that, I have a good chance for gold. The Thai girl's personal best is 4.21m but that doesn't always mean she'll hit that. In a competition, you never know what's going to happen."

She is nursing a strained back from a warm-up meet in KL last month, but remains confident of her chances. She said: "I honestly didn't expect to be performing at the level I am now and clearing 3.91m. I'm grateful things are falling into place and I can't wait for my event. I have nothing to lose."