The team said in a press release that a timeline for his recovery will be determined following surgery on Wednesday in New York.
Walker, 24, flew to New York to have a second opinion on his knee. The Hornets say that Dr. David Altchek confirmed team orthopedic physician Marcus Cook's previous diagnosis, although the team previously only listed Walker as having a cyst on the knee.
It's possible the surgery could end Walker's season.
According to Dr. Calin Moucha, the associate chief of joint replacement surgery for the Icahn School of Medicine at Mount Sinai Hospital, the range of recovery time for a player with that type of injury is typically between four weeks to five months depending on the location and configuration of the tear.
Moucha, who is not performing the surgery, said if the meniscus simply needs to be debrided -- or cleaned out -- Walker would likely be back in four to six weeks. However, if the meniscus needs to be repaired, Moucha said Walker could miss five to six months.
The fourth-year point guard is Charlotte's leading scorer this season, averaging 18.8 points per game and is tied for sixth in the NBA in assists per turnover ratio (3.1).
Walker has averaged 23 points in last his 21 games, and scored 20 or more points in 14 of those contests.
Coach Steve Clifford said after Monday's practice that if Walker is out any length of time it would be a "significant hit" to the Hornets.
"He's been by far our best player," Clifford said. "You see it every year, every team. The Cavs without LeBron (James). Oklahoma City without (Kevin) Durant. ... It always starts at the top of your roster and that's why most teams that are winning have a superstar. He's playing at a real high level."
The 6-foot-1 Walker has missed three of the team's last five games with the knee issue.
Brian Roberts will continue to start in his place.
Roberts started 42 games last year for New Orleans and led the Hornets with 17 points in a 76-71 win over the New York Knicks on Saturday night.
Walker is just part of the team's injury problems.
The Hornets also announced Monday center Bismack Biyombo has been diagnosed with a bone bruise in his right knee and will miss about 10 days and forward Marvin Williams has a broken nose and a concussion.
Both Biyombo and Williams were injured in the win over New York.
Biyombo took over as the temporary starter after Al Jefferson injured his groin. He'll be reevaluated in 10 days.
Williams took an elbow to the face against the Knicks and did not return. He cannot return to practice or game action until he passes the NBA concussion protocol.